Medical students’ characteristics as predictors of career practice location: retrospective cohort study tracking graduates of Nepal’s first medical college | BMJ
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Research Medical students’ characteristics as predictors of career practice location: retrospective cohort study tracking graduates of Nepal’s first medical college BMJ 2012; 345 doi: 10.1136/bmj.e4826 (Published 14 August 2012) Cite this as: BMJ 2012;345:e4826 Undergraduate Epidemiologic studies Article Related content Read responses (2) Article metrics Mark Zimmerman, executive director1, Rabina Shakya, administrative assistant1, Bharat M Pokhrel, professor, head of research committee2, Nir Eyal, assistant professor3, Basista P Rijal, professor, assistant dean2, Ratindra N Shrestha, professor, assistant dean2, Arun Sayami, professor, dean21Nick Simons Institute, Box 8975, EPC 1813, Kathmandu, Nepal2Institute of Medicine, Kathmandu, Nepal3Harvard Medical School, Boston, MassachusettsCorrespondence to: M Zimmerman markz{at}nsi.edu.npAccepted 6 July 2012AbstractObjective To determine, in one low income country (Nepal), which characteristics of medical students are associated with graduate doctors staying to practise in the country or in its rural areas.Design Observational cohort study.Setting Medical college registry, with internet, phone, and personal follow-up of graduates.Participants 710 graduate doctors from the first 22 classes (1983-2004) of Nepal’s first medical college, the Institute of Medicine.Main outcome measures Career practice location (foreign or in Nepal; in or outside of the capital city Kathmandu) compared with certain pre-graduation characteristics of medical student.Results 710 (97.7%) of the 727 graduates were located: 193 (27.2%) were working in Nepal in districts outside the capital city Kathmandu, 261 (36.8%) were working in Kathmandu, and 256 (36.1%) were working in foreign countries. Of 256 working abroad, 188 (73%) were in the United States. Students from later graduating classes were more likely to be working in foreign countries. Those with pre-medical education as paramedics were twice as likely to be working in Nepal and 3.5 times as likely to be in rural Nepal, compared with students with a college science background. Students who were academically in the lower third of their medical school class were twice as likely to be working in rural Nepal as those from the upper third. In a regression analysis adjusting for all variables, paramedical background (odds ratio 4.4, 95% confidence interval 1.7 to 11.6) was independently associated with a doctor remaining in Nepal. Rural birthplace (odds ratio 3.8, 1.3 to 11.5) and older age at matriculation (1.1, 1.0 to 1.2) were each independently associated with a doctor working in rural Nepal.Conclusions A cluster of medical students’ characteristics, including paramedical background, rural birthplace, and lower academic rank, was associated with a doctor remaining in Nepal and with working outside the capital city of Kathmandu. Policy makers in medical education who are committed to producing doctors for underserved areas of their country could use this evidence to revise their entrance criteria for medical school.IntroductionDoctors tend to migrate from medically less well served areas to better served areas. This paradoxical flow occurs over a continuum that includes internal migration (often from rural to urban areas) and external migration (from low income to high income countries). Both result in adverse outcomes for patients in the areas of origin.1 2 In recent policy documents, the World Health Organization and others have issued calls to “build the evidence base” on retention of healthcare workers in underserved areas.3 4 5 6Existing retention studies, mainly from high income countries, report associations of rural upbringing and male sex with career practice in a rural setting.7 8 9 10 International migration studies likewise usually derive their data from destination (high income) countries, and none has compared the rates of emigration with medical students’ characteristics.11 12 13 14 15 16 17Nepal is an Asian country with a population of 28 million; its mountainous topography and poverty (annual gross domestic product $300 (£193; €245) per capita) pose barriers to adequate healthcare. According to WHO’s statistics, Nepal ranks near the bottom of countries in the region,18 and like many other nations it struggles with inequitable distribution of its health workers.19 In 1978 Nepal’s Institute of Medicine, which was founded with an ethos of serving the country’s remote population, admitted Nepal’s first class of medical students. Initially, the institute selected students from rural Nepal and admitted only those with a paramedical background. In Nepal, two possible pre-medical tracks exist: “paramedical” education involves three years of training after high school and leads to clinical practice; “intermediate science” involves two years of purely classroom education with no medical exposure. Although it remained Nepal’s sole medical college for 13 years (and was still the country’s premier medical college at the time of this study), the Institute of Medicine gradually shifted away from its original selection system, eventually taking only intermediate science students on the basis of their entrance examination scores.Certain characteristics of medical students—sex, age at matriculation, rural upbringing, type of pre-medical education, and academic rank—may be associated with doctors choosing to practise in Nepal rather than abroad or in Nepal’s rural areas rather than in the capital city of Kathmandu. To test this hypothesis, we tracked the graduate doctors of the first 22 classes (1983-2004) of the Institute of Medicine to determine their eventual locations of practice. If associations between medical students’ characteristics and career practice location are validated, they could be used to construct admission criteria for medical schools that favour subsequent practice in less well served areas.MethodsSelection of medical student related factorsTo determine which characteristics of medical student predicted location of practice in underserved areas, we analysed seven factors. We chose to study place of birth, place of high school, and sex to test the conclusions of previous studies done in high income countries. We also included type of pre-medical education because of the undocumented observation in Nepal that more doctors from a paramedical background seemed to stay in Nepal. We included year of graduation in the analysis to account for historical trends. Finally, we included final academic score and age at matriculation because these were potential confounders.Data collectionWe did this study in partnership with the Nepal Institute of Medicine’s Dean’s Office, Research Department, and Examination Control Division. We collected data continuously from August 2008 to July 2010 (24 months) in three phases: a review of records at the Institute of Medicine, a written questionnaire from graduates, and reporting by classmates. The study depended on extensive cooperation from the Institute of Medicine and its network of alumni.We chose to collect data covering the institute’s first to 22nd graduating classes (1983 to 2004), thereby leaving a minimum of four years of post-graduation follow-up. This was to allow for “settling” in a doctor’s practice location. We derived data from three sources.Institute of Medicine recordsThe Examination Control Division provided complete lists of the first 22 entering classes of its Bachelor of Medicine Bachelor of Surgery (MBBS) student doctors. Data included class number and graduation year, name, sex, type of pre-medical education, and final examination score.Questionnaire from graduatesWe developed a standardised three page questionnaire and uploaded it for online response. We recruited respondents through newspaper advertisements, the NepalNews internet site, social networks, and personal contacts. If no response came through internet or email, we used phone interviews to complete questionnaires. Questionnaire data included each doctor’s class number, birthplace, place of high school, and pre-medical training (paramedical or intermediate science); spouse’s birthplace; postgraduate work history, current practice location, and postgraduate degrees; perceived personal factors influencing career practice location; and contact information for classmates.Because after one year we had received filled questionnaires from just over half of all graduates, we added a “mop-up” phase. This final phase, which simultaneously collected questionnaires and took classmates’ reports, required an additional 12 months to complete.Classmates’ reportsFor those doctors who did not complete questionnaires, we used multiple methods to collect “proxy” information from fellow graduates. All questionnaire respondents received a list of non-responders from their class and from the four nearest classes. We also re-contacted questionnaire respondents by phone to ask about classmates. In each class, we interviewed multiple graduates to provide cross validation. Data in this phase included only current practice location.ParticipantsThe first 22 classes of Nepal’s Institute of Medicine had 727 graduates. Of this total, we obtained filled data questionnaires from 436 (60.0%), classmates’ reports on an additional 286 (39.3%), and no information on 5 (0.7 %) (fig1?). Twelve were reported to have died.View larger version:In a new windowDownload as PowerPoint SlideFig 1 Study participantsOur data contained two subsets. For the 60% (n=436) of graduates who completed questionnaires, we had information on their career location as well as all seven medical student related factors. For the 38% (n=274) of graduates whose career location came from classmates’ reports, we had data for only four of the seven factors (sex, type of pre-medical education, year of graduation, and final examination score). Table 1? shows the compilation of both data subsets, including the characteristics of all 710 graduates. The regression analyses include only those graduates for whom we had data on all seven factors (the “filled questionnaire” subset). We did case-wise deletion for all analyses and made no attempt to impute missing data. All numbers in tables reflect the number of observations with complete data available for analysis.View this table:View PopupView InlineTable 1 Characteristics of Institute of Medicine graduates. Values are numbers (row percentages) of doctors in each practice locationData analysisTo explore the relation between medical students’ characteristics and doctors’ current location of practice, we did two separate logistic regressions. The first compared doctors who remained in Nepal with those who practised in foreign countries (reference group). The second compared doctors who practised in Nepal’s rural districts with those who practised in Kathmandu (reference group). We report odds ratios for the likelihood of remaining in Nepal and for working in the rural districts for both unadjusted and adjusted models. Fully adjusted models include all the variables in table 1?. Because of the small sample size, we excluded respondents whose birthplace or place of high school graduation was outside of Nepal (foreign). We modelled academic class rank as a continuous variable standardised within the graduating class. We also modelled age at matriculation as a continuous variable. We used SAS 9.2 for all analyses.ResultsPractice locationOf 710 living graduates, we found that 193 (27.2%) worked in districts of Nepal outside of Kathmandu, 261 (36.8%) in Kathmandu, and 256 (36.1%) outside of Nepal. Of the 256 graduates working outside Nepal, we received reports on the specific country for all of them: 188 (73%) doctors were working in the United States, 20 (8%) in the United Kingdom, 8 (3%) in Australia, 8 (3%) in South Africa, and 32 (13%) in other countries (table 2?).View this table:View PopupView InlineTable 2 Foreign country practice locationFigure 2? shows the proportion of doctors located in different countries by their era of graduating class. The number of Institute of Medicine graduates going to the United States increased over the period that this study covered, while decreasing numbers went to the UK and to other countries. We noted some “clustering” of graduates within an era: for example, a group of graduates in the early classes went to South Africa, and in later years a group went to China.View larger version:In a new windowDownload as PowerPoint SlideFig 2 Country location by graduation eraOf the 436 graduates who filled in questionnaires, 332 (76%) were in Nepal; of the 274 whose location data came by classmates’ reports, 122 (44%) were in Nepal. That is, full questionnaire data was more readily available for those doctors whom we could contact directly inside the country. Although these two data subsets (filled questionnaire and classmate reported) thus differed in terms of practice location, for the four characteristics of medical students available for all graduates, the odds ratios for the two subsets were similar.Factors associated with practice locationOver the span of 22 classes, doctors graduating in later years were more likely to practise in foreign countries (53% of era 3 students versus 14% of era 1 students) and less likely to practise in rural Nepal (7% v 38%) (table 1?). Male students made up 88.3% of all graduates. Compared with their female classmates, men were twice as likely to remain in Nepal and to work in rural areas.For the first five classes (era 1), the institute admitted only students with a paramedical background; from the sixth class onwards, intermediate science students were admitted. Compared with those with science background, students with a paramedical background were twice as likely to remain in Nepal and 3.5 times as likely to practise in rural Nepal.To graduate, students at the institute had to pass an academic examination (written and oral), and this final examination score determined their rank in the class. Compared with students ranked in the top third of their class, those who ranked in the lower third of their classes were twice as likely to remain in rural areas of the country.Data on birthplace, place of high school, and age at matriculation were available only for the subset of doctors who completed questionnaires. Students with rural birthplace and graduation from rural high school were three to four times as likely to work in rural Nepal, compared with students raised in Kathmandu.For a contemporaneous comparison between students with paramedical and intermediate science backgrounds, we analysed the subset of graduates from the era 1988 to 2002—the period of mixed intake of the two pre-medical streams. For this period, those with a paramedical background were twice as likely to eventually work in Nepal (79% v 42%) and three times as likely to be in rural Nepal (42% v 13%) compared with those with a science background.Table 3? gives the odds ratio for doctors remaining in Nepal (versus emigrating to work in a foreign country) for each of the seven medical student related factors. Of 351 graduates included in this analysis, 71 (20%) were working in foreign countries. The unadjusted odds ratios for the subset of doctors who provided complete data were similar to the crude ratios for the four common factors (graduation era, sex, pre-medical education, and final examination score) shown in table 1? (the whole cohort of graduates).View this table:View PopupView InlineTable 3 Odds ratio of remaining in Nepal (versus working in foreign countries) (n=351)When adjusted for each of the other characteristics of medical students, the only factor found to have a significant independent association with retention in Nepal was paramedical background. After adjustment, the odds ratio for paramedical background (versus intermediate science) was 4.4 (95% confidence interval 1.7 to 11.6).Among those doctors who stayed in Nepal, table 4? gives the odds ratio for working in rural areas (versus in Kathmandu). Without adjustment, all of the factors except sex were associated with working in rural Nepal. The unadjusted odds ratios were again similar to the crude ratios for these same factors in table 1? (the total sample). When adjusted for each of the other characteristics, the two factors found to have a significant independent association with rural retention were rural birthplace (odds ratio 3.8, 1.3 to 11.5) and older age at matriculation (1.1, 1.0 to 1.2).View this table:View PopupView InlineTable 4 Odds ratio of working in rural Nepal (versus Kathmandu) (n=280)DiscussionWe tracked graduates of Nepal’s first medical college, the Institute of Medicine, to their current locations of practice. Diverse modes of communication applied over a two year period, a tight knit alumni network, and the cooperation of the college authorities enabled us to locate 98% of the doctors 4-26 years after their graduation. They were approximately distributed in thirds: located in Nepal’s rural districts, in the capital Kathmandu, or in foreign countries. The institute’s changing admission policy over the decades provided an internal comparison to study the effects of different intake criteria for medical students on the eventual practice location of graduates. We found an association between rural birthplace, paramedical pre-medical education, lower academic rank, male sex, and older age at matriculation and eventually working in a relatively underserved area.The WHO’s and other recent reviews on international and internal migration of health workers highlight the paucity of evidence, particularly for low income countries and with regard to potential interventions.3 4 5 6 20 Most studies on international migration use databases from destination (high income) countries rather than indexing from source countries.11 12 14 Dovlo studied Ghanaian medical students and found that 9.5 years after graduation, 75% had left their home country.13 Two South African studies located doctors by their postal addresses, and one found that rural service was associated with rural birthplace.9 21 Others mentioned successful retention among graduates of certain medical colleges in low income countries, but evidence was not presented.22 23 24Across the Institute of Medicine’s first 22 classes (1983-2004), graduates from later years were more likely to work abroad or, if they stayed in Nepal, to work in Kathmandu. It is tempting to relate their foreign migration to the increased availability of postgraduate training posts in the United States or to Nepal’s civil war (1996-2006). However, in our study, location of practice was not independently associated with a student’s era of graduation but was linked to several other factors.High income countries have documented the association of rural upbringing with doctors’ eventual rural practice, although in those cohorts selection of students on the basis of rural background was usually part of a mixed intervention that included scholarships and career practice incentives.7 8 25 26 A review study found that male sex was also associated with rural practice of doctors.27In Nepal, we collected data on factors that could be evaluated at the time of medical school attendance: age at matriculation, sex, places of birth and high school, type of pre-medical education, and final academic score/class rank. The data on rural background and matriculation age were available only for the 60% of the graduates who completed questionnaires; data on the other four factors were available for 98% of the institute’s graduates.Our study validated the independent association of rural birthplace with the eventual rural practice of the doctor. Compared with other studies, in Nepal this association was not complicated by overlaid incentives for rural practice: few such programmes existed in the country over the previous decades. Students who have spent all or part of their childhood in a rural setting may feel more at home in a remote medical practice. Selecting students with this background does not guarantee eventual rural practice, but it seems to increase the likelihood.The Institute of Medicine began by admitting only students with a paramedical background (usually health assistants) whose pre-medical training and work experience were in clinical medicine; it later also admitted pre-medical science students. We found a significant, independent association between students from a paramedical background and doctors remaining to work in Nepal. In other words, the alternative pre-medical track of intermediate science made it more likely that an admitted student would eventually establish a practice abroad. This association was independent of historical era and persisted for the years (1988-2002) when students from both types of background were admitted into the same classes.Paramedical students’ previous experience of working in rural healthcare institutions may have encouraged them to choose to work (and stay) in underserved areas after they became doctors. Vietnam and China have medical school programmes that enable paramedical intake.3 Although Nepal’s Institute of Medicine did not use any “catch-up” academic programmes, others have reported successful bridging programmes that bring students from alternative pathways up to an acceptable academic standard.24 28WHO categorised interventions to redress inequitable distribution of doctors into four areas: education, regulation, financial incentives, and personal support.3 Our study focused on factors that could be targeted at the time of selection for medical school (the education phase).Although each of the six medical student related factors in our study—along with earlier era of graduation—was associated with practice either in Nepal or in its rural areas, the multivariable analyses showed that these were mostly clustered, rather than isolated, factors. For example, a common profile of a paramedical student included rural upbringing, later entry into medical school, and lower academic rank. One could interpret this as being a student with broader practical experience but not necessarily the highest academic prowess or ability to take tests. The experience of the Institute of Medicine would argue that this did not promote mediocrity in medical practice: rather, over the decades, both the institute’s paramedical graduates and its science graduates have a solid track record in a wide range of practice settings.29 Furthermore, we found that higher academic rank in the class was not independently associated with foreign migration but was clustered with other factors. Selection for medical school based less on entrance examination scores and more on non-academic factors could produce a graduating class of doctors more likely to serve the wider, local population, without forfeiting professional excellence.LimitationsOur study has several limitations. Firstly, for our regression analyses, we used the data from the 60% of graduates who provided full information on questionnaires. Because that group was somewhat more likely to be in Nepal at the time of our study, they may not fully represent the whole population of graduates. Nevertheless, for the students’ characteristics that we measured, the crude ratios of the full cohort were very similar to the odds ratios of the questionnaire subset.Secondly, as a measure of academic ability, we had access to final academic examination scores. Entrance examination scores would have been more relevant to selection criteria for medical school.Thirdly, we placed doctors into three categories of location of practice: Nepal districts, Kathmandu, and foreign. Because Nepal has other cities, the first category is not purely “rural.” However, a distinct drop-off in medical service and living conditions occurs on leaving the city of Kathmandu.Finally, we located doctors only at one point in time. This left open the possibility that doctors were still in transit when we located them or that they had worked in several sectors over their career. We tried to minimise this source of error by leaving a minimum of four years’ lead time from graduation to our study contact time. Our experience is that most Nepalese doctors do not move to and from overseas locations after a period of settling.Application of findingsThe findings of our retrospective study in one low income country in Asia need to be validated in others settings, perhaps through interventions in selection for medical school. Policy makers in medical education who are committed to producing doctors for underserved populations could consider adjusting their selection of students. An intake process that gives higher emphasis to rural birthplace, rural high school, and paramedical education—while using an academic minimum cut-off criterion, rather than entrance scores—may result in more of the graduating class “staying home.”What is already known on this topicMigration of doctors from low income to high income countries and from rural to urban areas is extensiveIn high income countries, doctors with rural backgrounds are more likely to work in rural locations of their own countriesWhat this study addsFor Nepalese graduate doctors, an association existed between rural birthplace, paramedical pre-medical education, lower academic rank, male sex, and older age at matriculation and eventually working in a relatively underserved areaPolicy makers in medical education who are committed to producing doctors for underserved areas of their country could use this evidence to revise entrance criteria for medical schoolNotesCite this as: BMJ 2012;345:e4826FootnotesWe acknowledge the contributions of Robert Gerzoff, who did the statistical analysis of the data. We also acknowledge Dikshya Adhikari for recruitment of participants and Arjun Karki for the conceptual challenge.Contributors: MZ and BMP were involved in the conception and design of the study; data collection, analysis, and interpretation; and writing the paper. RS was involved in study conception and design and in data collection, analysis, and interpretation. NE was involved in study design, data analysis and interpretation, and writing the paper. BPR and RNS were involved in study conception and in data collection and interpretation. AS was involved in study conception and design and in data interpretation. MZ is the guarantor.Funding: Funding came entirely from the Nick Simons Institute, a charitable organisation that works to train and support healthcare workers for rural Nepal (www.ndi.edu.np). Neither the Nick Simons Institute nor the authors stands to receive material gain from the publication of this study. The Nick Simons Institute carried out this study as part of its mission to train and support healthcare workers for rural Nepal. It will use the study results to lobby for changes in medical education policy, in Nepal and internationally.Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: the submitted work was supported by the Nick Simons Institute; BMP, BPR, RNS, and AS are all on the faculty of the Institute of Medicine; AS is the Dean; no other relationships or activities that could appear to have influenced the submitted work.Ethical approval: The Institute of Medicine (Nepal) Research Committee, which functions as that institution’s ethics review board, approved this study in July 2008. The Research Committee also approved the “mop-up phase” and use of data from non-responding doctors.Data sharing: The spreadsheet containing the data for this study can be downloaded from ftp://nsi.edu.np (user name: iom_data@nsi.edu.np; password: admin123).This is an open-access article distributed under the terms of the Creative Commons Attribution Non-commercial License, which permits use, distribution, and reproduction in any medium, provided the original work is properly cited, the use is non commercial and is otherwise in compliance with the license. See: http://creativecommons.org/licenses/by-nc/2.0/ and http://creativecommons.org/licenses/by-nc/2.0/legalcode.References?Joint Learning Initiative. Human resources for health: overcoming the crisis. Harvard College, 2004 (available at www.healthgap.org/camp/hcw_docs/JLi_Human_Resources_for_Health.pdf).?Speybroeck N, Kinfu Y, Dal Poz MR, Evans DB. 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Rural Remote Health2012;12:1835.OpenUrlMedline?Huish R. Going where no doctor has gone before: the role of Cuba’s Latin American School of Medicine in meeting the needs of some of the world’s most vulnerable populations. Public Health2008;122:552-7.OpenUrlCrossRefMedlineWeb of Science?Iputo JE. Faculty of Health Sciences, Walter Sisulu University: training doctors from and for rural South African communities. MEDICC Review Fall2008;10(4):25.OpenUrlWeb of Science?Eley D, Baker P. Does recruitment lead to retention? Rural clinical school training experiences and subsequent intern choices. Rural Remote Health2006;6:511.OpenUrlMedline?Walker JH, Dewitt DE, Pallant JF, Cunningham CE. Rural origin plus a rural clinical school placement is a significant predictor of medical students’ intentions to practice rurally: a multi-university study. Rural Remote Health2012;12:1908.OpenUrlMedline?Laven G, Wilkinson D. Rural doctors and rural backgrounds: how strong is the evidence? A systematic review. Aust J Rural Health2003;11:277-284.OpenUrlCrossRefMedline?Polasek O, Kolcic I. Academic performance and scientific involvement of final year medical students coming from urban and rural backgrounds. Rural Remote Health2006;6:530.OpenUrlMedline?Dixit H. Nepal’s quest for health. Educational Publishing House, 2005. Open access PDFEasy ReadPress releaseRespond to this article Tweet Services Email to friendDownload to citation managerAdd article to BMJ portfolioRequest permission Citations Find similar articles in PubMedArticles by Mark ZimmermanArticles by Rabina ShakyaArticles by Bharat M PokhrelArticles by Nir EyalArticles by Basista P RijalArticles by Ratindra N ShresthaArticles by Arun SayamiCiting articles via Web of ScienceCiting articles via Scopus Social bookmarking CiteULike Connotea Del.icio.us Digg Facebook Mendeley Reddit Technorati Twitter Stumbleupon Latest jobsUK jobsInternational jobsUK jobs AXESS LTD, EU MEDICAL ADVISER. 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Predicting early death in patients with traumatic bleeding: development and validation of prognostic model | BMJ
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Research Predicting early death in patients with traumatic bleeding: development and validation of prognostic model BMJ 2012; 345 doi: 10.1136/bmj.e5166 (Published 15 August 2012) Cite this as: BMJ 2012;345:e5166 Epidemiologic studies Coma and raised intracranial pressure Hypertension Article Related content Read responses (2) Article metrics Pablo Perel, senior clinical lecturer1, David Prieto-Merino, lecturer, medical statistics2, Haleema Shakur, senior lecturer1, Tim Clayton, senior lecturer, medical2, Fiona Lecky, clinical professor3, honorary professor4, honorary consultant5, Omar Bouamra, medical statistician6, Rob Russell, senior lecturer7, Mark Faulkner, paramedic advisor8, Ewout W Steyerberg, professor9, Ian Roberts, professor11Clinical Trials Unit, London School of Hygiene and Tropical Medicine, London WC1E 7HT, UK2Medical Statistics Department, Epidemiology and Population Health Faculty, London School of Hygiene and Tropical Medicine3University of Sheffield, Sheffield, UK4University of Manchester, Manchester, UK5Salford Royal Hospitals NHS Foundation Trust Trauma Audit and Research Network, Salford, UK6Trauma Audit and Research Network, Health Science Research Group, School of Community Based Medicine, University of Manchester, Salford Royal Hospital, Salford, UK7UK Royal Centre for Defence Medicine, Birmingham, UK8London Ambulance Service and London Trauma Office9Department of Public Health, Center for Medical Decision Making, Erasmus MC, Rotterdam, NetherlandsCorrespondence to: P Perel London School of Hygiene & Tropical Medicine, Keppel Street, pablo.perel{at}lshtm.ac.ukAccepted 11 July 2012AbstractObjective To develop and validate a prognostic model for early death in patients with traumatic bleeding.Design Multivariable logistic regression of a large international cohort of trauma patients.Setting 274 hospitals in 40 high, medium, and low income countriesParticipants Prognostic model development: 20?127 trauma patients with, or at risk of, significant bleeding, within 8 hours of injury in the Clinical Randomisation of an Anti?brinolytic in Signi?cant Haemorrhage (CRASH-2) trial. External validation: 14?220 selected trauma patients from the Trauma Audit and Research Network (TARN), which included mainly patients from the UK.Outcomes In-hospital death within 4 weeks of injury.Results 3076 (15%) patients died in the CRASH-2 trial and 1765 (12%) in the TARN dataset. Glasgow coma score, age, and systolic blood pressure were the strongest predictors of mortality. Other predictors included in the final model were geographical region (low, middle, or high income country), heart rate, time since injury, and type of injury. Discrimination and calibration were satisfactory, with C statistics above 0.80 in both CRASH-2 and TARN. A simple chart was constructed to readily provide the probability of death at the point of care, and a web based calculator is available for a more detailed risk assessment (http://crash2.lshtm.ac.uk).Conclusions This prognostic model can be used to obtain valid predictions of mortality in patients with traumatic bleeding, assisting in triage and potentially shortening the time to diagnostic and lifesaving procedures (such as imaging, surgery, and tranexamic acid). Age is an important prognostic factor, and this is of particular relevance in high income countries with an aging trauma population.IntroductionEach year around 4 million people die worldwide from unintentional injury and violence, and tens of millions are left permanently disabled. Most of the victims are from low and middle income countries.1 Although many of these deaths occur at the scene of the injury, 44% are estimated to occur after admission to hospital.2Severe bleeding accounts for about one third of in-hospital deaths due to trauma and is an important contributory factor for other causes of death, particularly head injury and multi-organ failure.3 Failure to start appropriate early management in bleeding trauma patients is a leading cause of preventable death from trauma.4 Triage criteria that allow the rapid identification of patients at high risk have the potential to reduce mortality from trauma. Recent evidence that the early administration of tranexamic acid substantially reduces mortality in bleeding trauma patients further underscores the clinical importance of the timely identification of life threatening bleeding.5 However, any such early prediction would have to be based on variables that can be readily measured soon after injury. Several clinical variables related to the physiological response to reduced intravascular volume predict the risk of death in bleeding trauma patients. These include blood pressure, capillary refill time, level of consciousness (Glasgow coma score), heart rate, and respiratory rate.6 Because all of these variables are of limited predictive value when considered in isolation, prognostic models that combine variables are needed for better predictive accuracy.7 8 9 An accurate and user friendly prognostic model to predict mortality in patients with traumatic bleeding could assist doctors and paramedics in pre-hospital triage, whether in civilian or battlefield settings; its use could shorten the time to diagnostic and lifesaving procedures (such as surgery and tranexamic acid). We have previously published a prognostic model for patients with traumatic brain injury, which was accurate, user friendly, and clinically useful for supporting physicians’ decision making.10 11Existing prognostic models for bleeding trauma patients are limited.12 Most were developed using data collected many decades ago and have methodological limitations. Models based on contemporary data are needed, as treatment practices have changed and the age of trauma patients has increased in high income countries. Furthermore, although most deaths due to trauma occur in low and middle income countries, most prognostic models are based on data from high income countries.12 We aimed to develop a simple prognostic model that could be used at the point of care to estimate risk of death in patients with traumatic bleeding.MethodsModel developmentFor the development of the prognostic model, we involved potential users from three settings: pre-hospital, battlefield, and emergency departments. We held meetings with paramedics, military doctors, and consultants in emergency medicine to identify variables and interactions that they considered important and convenient for their settings and to obtain information on how to present the prognostic model in a user friendly format.We included patients from the Clinical Randomisation of an Anti?brinolytic in Signi?cant Haemorrhage (CRASH-2) trial.13 The trial included 20?127 trauma patients with, or at risk of, significant bleeding, within eight hours of injury, and took place in 274 hospitals in 40 countries. The primary outcome was all cause mortality. Patients’ outcomes were recorded at discharge, at death in hospital, or 28 days after injury, whichever occurred first.PredictorsWe took variables to be analysed as potential predictors from the patients’ entry forms completed before randomisation. Variables included in the entry form for the CRASH-2 trial can be divided into patients’ demographic characteristics (age and sex), characteristics of the injury (type of injury and time from injury to randomisation), and physiological variables (Glasgow coma score, systolic blood pressure, heart rate, respiratory rate, and central capillary refill time).Age was recorded as a continuous variable measured in years. Type of injury had three categories—penetrating, blunt, or blunt and penetrating—but we analysed it as “penetrating” or “blunt and penetrating.” Time from injury was recorded as a continuous variable measured in hours. The five physiological variables were recorded according to usual clinical practice. For each of these variables, the value given on the entry form was the first measurement taken at hospital admission.Multivariable analysisWe did complete case analysis, as the amount of missing data was very low in CRASH-2. We initially included all candidate predictors in the multivariable logistic regression. We adjusted analyses for treatment by including treatment allocation as a covariate in the models. We also included a variable for economic region (that is, low, middle, or high income country, as defined by the World Bank).14 We used logistic regression models with random intercepts by country. We initially analysed continuous variables as linear terms. We assessed departure from linearity graphically and by adding quadratic and cubic terms into the model. We specifically explored interactions by age and by type of injury. We dichotomised time since injury into less than or more than three hours, as the effect of this variable was reasonably well captured by treating it as binary.We used a backward stepwise approach. Firstly, we included all potential prognostic factors and interaction terms that users considered plausible. These interactions included all potential predictors with type of injury, time since injury, and age. We then removed, one at a time, terms for which we found no strong evidence of an association, judged according to the P values (<0.05) from the Wald test. Each time, we calculated a log likelihood ratio test to check that the term removed did not have a big effect in the model. Eventually, we reached a model in which all terms were statistically significant. We used the R software environment (version 2.13.1; R Foundation for Statistical Computing, Vienna, Austria).PerformanceWe assessed the predictive ability of the prognostic model in terms of calibration and discrimination. Calibration indicates whether observed risks agree with predicted risks; we assessed this graphically by plotting the observed outcomes versus the predicted probabilities of the outcomes. Discrimination indicates whether patients at low risk can be separated from those at high risk; we assessed this by using a concordance (C) statistic.15 We assessed optimism in the performance by bootstrap re-sampling. We drew 200 samples with replacement from the original data, with the same size as the original derivation data. In each bootstrap sample, we repeated the entire modelling process, including variable selection. We averaged the C statistics of those 200 models in the bootstrap samples. We then estimated the average C statistic when each of the 200 models was applied in the original sample. The difference between the two average C statistics indicated the “optimism” of the C statistic in our prognostic model.15External validationFor the external validation, we used the data from the Trauma Audit and Research Network (TARN). Membership is voluntary and includes 60% of hospitals receiving trauma patients in England and Wales and some hospitals in Europe. Data are collected on patients who arrive at hospital alive and meet any of the following criteria: death from injury at any point during admission, stay in hospital of longer than three days, need for intensive or high dependency care, need for inter-hospital transfer for specialist care.We excluded patients with isolated closed limb injuries and those over 65 years old with isolated fractured neck of femur or pubic ramus fracture. The physiological data available in TARN are identical to those in CRASH-2, in that for every patient the heart rate, systolic blood pressure, Glasgow coma score, respiratory rate, and capillary refill time on arrival are entered by the hospital data coordinators. For each patient, the volume of blood loss is estimated. This is done by allocating an estimated percentage of total volume of blood lost to each injury code in the abbreviated injury scale dictionary by blinded, then consensus, agreement from two emergency physicians. This estimation is based on previous work on blood loss in specific injuries.16We selected adult (age over 15 years at the time of injury) patients presenting between 2000 and 2008 to hospitals participating in TARN. The definition of significant haemorrhage used in the CRASH-2 trial was not available, so we selected only patients with an estimated blood loss of at least 20%, whom we considered would be clinically comparable to the CRASH-2 patients.For the validation in the TARN dataset, we did multiple imputations to substitute the missing values of the predictors included in the prognostic model by using the procedure of imputation by chained equations in Stata Release 11. We applied the coefficients of the model developed in CRASH-2 with the estimated UK intercept to the five imputed datasets of TARN, obtaining five predictions of mortality for each patient in TARN. We then averaged over these five predictions to calculate calibration and discrimination.15Simple prognostic modelFor ease of use at the point of care, we developed a simple prognostic model. For this model, we included the strongest predictors with the same quadratic and cubic terms as used in the full model, adjusting for tranexamic acid.We presented the prognostic model as a chart that cross tabulates these predictors with each of them recoded in several categories. We made the categories by considering clinical and statistical criteria. In each cell of the chart, we estimated the risk for a person with values of each predictor at the mid-point of the predictor’s range for that cell. We then coloured the cells of the chart in four groups according to ranges of the probability of death: <6%, 6-20%, 21-50%, and >50%. We decided these cut-offs by considering feedback from the potential users of the simple prognostic model and by looking at previous publications.17 18ResultsTables 1? and 2? show the characteristics of the patients in the CRASH-2 and TARN datasets. In the CRASH-2 trial, most patients were men and the median age was 30 years. Patients who died were on average older and had lower systolic blood pressure, higher heart rate, and lower Glasgow coma score than those who did not. Few data were missing for all the variables. In comparison, the patients from TARN were older (median age 39 years) and had a higher systolic blood pressure. In all, 3076 (15%) deaths occurred among the 20?127 CRASH-2 patients and 1765 (12%) in the 14?220 TARN patients.View this table:View PopupView InlineTable 1 Characteristics of CRASH-2 patientsView this table:View PopupView InlineTable 2 Characteristics of TARN patientsAge showed a positive and increasing association with risk of death; systolic blood pressure, heart rate, and respiratory rate showed U shaped relations; and Glasgow coma score had a negative association with risk of death (fig 1?). Table 3? shows that in the CRASH-2 trial, age was positively associated with mortality for each of the described causes of death; the highest relative increase was for vascular occlusive death.View larger version:In a new windowDownload as PowerPoint SlideFig 1 Association between continuous predictors and death among CRASH-2 patientsView this table:View PopupView InlineTable 3 Cause of death according to age in CRASH-2 patients. Values are numbers (percentages)We included quadratic or cubic transformations in the prediction model to accommodate for the departures from linearity. In the multivariable analysis, Glasgow coma score, systolic blood pressure, and age were the three strongest predictors. Heart rate, respiratory rate, and hours since injury were associated with mortality and were also included in the final model. Users considered all of these variables to be important. Patients in low and middle income countries were more likely to die in comparison with those in high income countries. Although capillary refill time was weakly associated with mortality, we did not include it in the prognostic model because in situations with poor visibility, such as in the battlefield, it is difficult to measure. In addition, capillary refill time was missing in more than 80% of the TARN patients. We found some evidence of a statistical interaction between Glasgow coma score and type of injury. Low Glasgow coma score was associated with worse prognosis for blunt injuries (see web appendix for details of the multivariable analysis).ValidationThe model showed a good internal validity, with a C statistic of 0.84 (fig 2?) and good calibration, except in patients at very high risk for whom the model over-predicted risk (fig 3?). Internal validation using bootstrapping showed a minimal decrease in the C statistic from 0.836 to 0.835. This indicates that very low over-optimism existed in the development of the model.View larger version:In a new windowDownload as PowerPoint SlideFig 2 Internal and external discrimination displayed by receiver operating characteristics curves. AUC=area under curve; PV+=positive predictive value; PV–=negative predictive valueView larger version:In a new windowDownload as PowerPoint SlideFig 3 Internal and external calibration of prognostic model by levels of predicted riskFor the external validation, we used the same variables as were included in the derivation model except hours since injury, as this variable had a very large number of patients with missing data. Discrimination was good (C statistic 0.88), and calibration was satisfactory (figures 2? and 3?).Model presentationThe prognostic model is available at http://crash2.lshtm.ac.uk/, so the risk of death can be obtained for individual patients. Entering the values of the predictors results in display of the expected risk of death at 28 days. For example, a 70 year old patient from a low income country, with a Glasgow coma score of 14, systolic blood pressure of 100 mm Hg, heart rate of 110 beats per minute, and respiratory rate of 35 breaths per minute, has a 32% probability of death at 28 days.Users also highlighted the importance of a simple prognostic model that could be used at the bedside. The simple prognostic model includes the three strongest prognostic variables: Glasgow coma score, systolic blood pressure, and age (see appendix). We developed different prognostic models for patients in low, middle, and high income countries and presented them as charts (fig 4?). These simple charts also showed good internal and external calibration (fig 5?).View larger version:In a new windowDownload as PowerPoint SlideFig 4 Chart to predict death in trauma patients. GCS=Glasgow coma scoreView larger version:In a new windowDownload as PowerPoint SlideFig 5 Internal and external calibration of simple chartDiscussionWe have developed and validated a prognostic model for trauma patients by using clinical parameters that are easy to measure. The model is available as a web calculator and can be used at the point of care in its simplified form. Separate models are available for patients from low, middle, and high income countries. This simple prognostic model could inform doctors about the risk of death and guide them in the early assessment and management of trauma patients.Strengths and limitationsOur study has several strengths. Our models were based on a prospective cohort of patients with traumatic bleeding, with standardised collection of data on prognostic factors, very little missing data, and low loss to follow-up. Unlike previous prognostic models, we explored more complex relations between continuous predictors and mortality and captured non-linear relations. All of these factors provide reassurance about the internal validity of our models. The large sample size in relation to the number of prognostic variables is also an important strength. Whereas most previous models were derived from single centre studies in high income countries, we developed separate models for low, middle, and high income countries. Unlike most previous models, we did an external validation in a large cohort of trauma patients. This confirmed the discriminatory ability of the model in patients from high income countries and showed good calibration.Another methodological strength was our use of imputation to replace missing data, which is rarely done in model validation studies. To the best of our knowledge, this is the only prognostic model for this population that is available in a web based calculator and a simplified chart that can be used at point of care. Importantly, we obtained advice from the potential users throughout its development.The study also has some limitations. The data from which the models were developed come from a clinical trial, and this could limit external validity. For example, patients were recruited within eight hours of injury, and we cannot estimate the accuracy of the models for patients evaluated beyond this time. Nevertheless, the CRASH-2 trial was a pragmatic trial that did not require any additional tests and therefore included a diversity of “real life” patients. In addition, the relation between predictors and outcome could be different in patients included in a clinical trial and in routine practice. However, the model’s good performance in a trauma registry population provides reassurance that any potential bias (if present) was small.Another limitation was that for the validation we used a cohort of trauma patients that were not equally defined, and we included them by using an estimation of the blood loss. In any case, this weakness could have led to underestimation of the accuracy of the model. Other potentially important variables such as pre-existing medical conditions, previous drugs, and laboratory measurements were not collected in the CRASH-2 trial and, therefore, not available for inclusion in the model. However, these are variables that are usually unavailable in the acute care trauma setting in which the model is intended to be used. The prognostic model predicts overall death rather than death due to bleeding, as death due bleeding was not available in the TARN dataset. However, bleeding would be expected to contribute to the other main causes of death in trauma patients. In addition, some deaths classified as “non-bleeding” could in fact have been due to bleeding. Finally, we observed some miscalibration; in particular, we observed overestimation for patients with predicted high risk in the internal validation. This finding might be related to the imprecision due to the low number of patients in the very high risk group. Only 100 patients (84 events) had a predicted risk of death above 90% in the CRASH-2 dataset. However, miscalibration at this high risk end of the spectrum (that is, 80% v 90% probability of death) is very unlikely to change clinical decision making.Implications of studyMany trauma protocols use blood pressure as the main criterion for determining who should receive urgent intervention. However, according to our model, a 75 year old with blunt trauma and a systolic blood pressure of 110 mm Hg, heart rate of 80 beats per minute, respiratory rate of 15 breaths per minute, and Glasgow coma score of 15 has a similar risk of death to a 45 year old patient with exactly the same parameters but a systolic blood pressure of 60 mm Hg. These findings have important practical implications. According to many trauma protocols, only the younger patient would receive urgent interventions such as tranexamic acid, and the older one would be denied this lifesaving intervention. The effect of age is particularly important, bearing in mind that in high income countries the average age of trauma patients is increasing. Data from TARN show that one quarter of the deaths due to trauma in England and Wales are in patients older than 70 years. The effect of age is likely to reflect the increased incidence of coexisting diseases, particularly cardiovascular diseases. Older patients are more likely to have coronary heart disease, and the decrease in oxygen supply associated with traumatic bleeding can increase the risk of myocardial ischaemia.19 Another potential explanation for the increased risk of death from vascular occlusive disease is related to the trigger of the inflammation process after trauma. After trauma, a potent inflammatory response involves increased serum concentrations of interleukin-1, interleukin-2, tumour necrosis factor-a, interleukin-6, interleukin-12, and interferon-?.20 In patients with traumatic bleeding, activation of plasmin occurs and plays a key role in the fibrinolytic response in the early hours after injury. Plasmin also has pro-inflammatory effects through the activation of cytokines, monocytes, neutrophils, platelets, and endothelial cells.21 Vascular risk may rise in short time periods of inflammatory responses to exposures such as infections or major surgery.22 Some of the observed prognostic role of age in trauma patients may be due to the inflammatory response to acute trauma, which might trigger acute vascular events, particularly in older patients who have a more widespread atherosclerotic condition. Furthermore, the prognostic role of age could be explained partially by a “self fulfilling prophecy” phenomenon, as age has been shown to be positively associated with “do not resuscitate” orders.23We acknowledge that estimating the risk of death in a trauma patient with bleeding is challenging. It is an ongoing process that uses not only physiological variables but other variables such as laboratory measurements and response to treatments. A prognostic model would never replace clinical judgment, but it can support it.We found that trauma patients in low and middle income countries were at higher risk of death compared with those from high income countries. We emphasise that the income classification refers to the country and not to individual patients. Some of the effect of classification of income might be the consequence of the differences in healthcare settings. Other studies have shown similar results, but to our knowledge this is the first one to include a large number of low and middle income countries.24 Although we did not have enough information to explore the causes of these differences, the rapid increase in the number of trauma patients combined with the lack of resources in poorer countries is probably among the most important reasons. Scaling up cost effective interventions in these settings could save hundreds of thousands of lives every year.Future researchThe relation between age and mortality needs further exploration. A better understanding of the mechanism by which age is associated with increasing mortality could lead to effective interventions to improve the outcome in this vulnerable population. As we were able to validate the model only in patients from high income regions, future studies should also explore its performance in low and middle income countries. Finally, future research should evaluate whether the use of this prognostic model in clinical practice has an effect on the management and outcomes of trauma patients.25What is already known on this topicFailure to start appropriate early management in patients with traumatic bleeding is a leading cause of preventable death from traumaAn accurate and user friendly prognostic model to predict mortality could assist the appropriate early management in bleeding trauma patientsThe methodological quality of published prognostic models is generally poor, sample sizes are small, and only a few models have included patients from low-middle income countries, where most deaths from trauma occurWhat this study addsAn accurate and user friendly prognostic model to predict mortality in trauma patients with bleeding has been developed and validatedThe prognostic model is available as a web based calculator, and a simplified model is available as a chart to be used at the bedsideThis prognostic model can assist in triage and can shorten the time to diagnostic and lifesaving procedures such as imaging, surgery, or tranexamic acidNotesCite this as: BMJ 2012;345:e5166FootnotesThis study will be published in full in the Health Technology Assessment journal series. We thank the CRASH-2 Trial Collaborators and the TARN Executive for making their data available. We also acknowledge the ambulance crew, military personnel, and emergency doctors who gave feedback in the different stages of development and validation of the prognostic model. PP and IR are members of the Medical Research Council Prognosis Research Strategy (PROGRESS) Partnership (G0902393/99558).Contributors: PP, HS, and IR designed the study. DP-M and OB analysed the data. PP and IR wrote the first draft of the paper. FL, RR, and MF gave feedback about the potential clinical use and format of the prognostic model. PP, DP-M, HS, TC, FL, OB, RR, MF, EWS, and IR contributed to writing the paper. PP, HS, IR, FL, and OB participated in the collection of data from which this manuscript was developed.Funding: This study was funded by the UK Health Technology Assessment programme (09/22/165). The views and opinions expressed are those of the authors and do not necessarily reflect those of the Department of Health.Competing interests: All authors have completed the Unified Competing Interest form at www.icmje.org/coi_disclosure.pdf (available on request from the corresponding author) and declare: no support from any organisation for the submitted work; no financial relationships with any organisation that might have an interest in the submitted work in the previous three years; no other relationships or activities that could appear to have influenced the submitted work.Ethical approval: The London School of Hygiene and Tropical gave medicine ethics approval for this study and the use of the CRASH-2 trial data. 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