Capture-recapture: a useful methodological tool for counting traffic related injuries?

Police and hospital data linkage for traffic injury surveillance: A systematic review

This systematic review examines studies of traffic injury that involved linkage of police crash data and hospital data and were published from 1994 to 2023 worldwide in English. Inclusion and exclusion criteria were the basis for selecting papers from PubMed, Web of Science, and Scopus, and for identifying additional relevant papers using PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) and supplementary snowballing (n = 60). The selected papers were reviewed in terms of research objectives, data items and sample size included, temporal and spatial coverage, linkage methods and software tools, as well as linkage rates and most significant findings. Many studies found that the number of clinically significant road injury cases was much higher according to hospital data than crash data. Under-estimation of cases in crash data differs by road user type, pedestrian cases commonly being highly under-counted. A limited number of the papers were from low- and middle-income countries. The papers reviewed lack consistency in what was reported and how, which limited comparability.

Estimation of the completeness of road traffic mortality data in Zambia using a three source capture recapture method

BACKGROUND

Accurate and reliable data are essential for tracking progress and evaluating the effectiveness of road safety intervention measures. However, in many low- and medium-income countries, good quality data on road traffic crashes are often difficult to obtain. This situation has led to an underestimation of the severity of the problem and distortions in trends when the reporting changes over time. This study estimates the completeness of road traffic crash fatality data in Zambia.

METHODS

Data from the police, hospitals, and the civil registration and vital statistics (CRVS) databases was collected for the period 1st January to 31st December 2020 and analyzed using a three-source capture-recapture technique.

RESULTS

A total of 666 unique records on mortalities as a result of road traffic crashes were collected from the three data sources during the period under review. The capture-recapture technique estimated the completeness of police, hospital, and CRVS databases to be 19%, 11% and 14% respectively. The combination of the three data sets was found to increase completeness to 37%. Based on this completion rate, we estimate that the actual number of people who died as a result of road traffic crashes in Lusaka Province in the year 2020 was approximately 1,786 (95% CI [1,448-2,274]). This corresponds to an estimated mortality rate of around 53 deaths per 100,000 population.

CONCLUSIONS

There is no single database contains complete data to provide a comprehensive picture of Lusaka province and by extension the country's road traffic injury burden. This study has shown how capture and recapture method can address this problem. It shows the need for the continuous review of the data collection processes and procedures in order to identify gaps and bottlenecks, improve efficiency, and increase the quality and completeness of road traffic data on injuries and fatalities. Based on the findings of this study, it is recommended that the city of Lusaka province and Zambia as a whole utilize more than one database for official reporting of road traffic fatalities to increase completeness.

Loss of years of healthy life due to road incidents of motorcyclists in the city of Medellin, 2012 to 2015

Objective

Determine the loss of years of healthy life due to road incidents of motorcyclists in the city of Medellin from 2012 to 2015.

Methods

Descriptive study with data on health care of injured motorcyclists and deaths adjusted with the Preston and Coale method, and OPS proportional distribution for the period 2012–2015. The years of life lost due to premature death (YLLs), years lived with disability (YLDs), and the disability-adjusted life years (DALYs) were calculated according to the new methodology designed for that purpose.

Results

The loss of years of healthy life due to road incidents of motorcyclists in the four-year period was 80,046 DALYs (823.8 per 100,000 inhabitants), with a higher proportion in men (81.3% and a ratio of 5 to 1 compared to women); the YLDs was 66.6% with marked differences in favor of men. There was nearly a 38% difference in the ages of 15 to 19 as well as a 19% difference from 30 to 49, compared to women. Premature death (YLLs) contributed to 33.4% of DALYs, with significant presentation in the above-mentioned age groups.

Conclusions

The greatest loss of years of healthy life due to road incidents of motorcyclists in Medellin was due to non-fatal injuries and was concentrated in young men. If the trend of motorcycle road incidents continues, both local and national road safety plans will fail to accomplish the expected results, especially among motorcycle users.

Road Safety in Low-Income Countries: State of Knowledge and Future Directions

Road safety in low-income countries (LICs) remains a major concern. Given the expected increase in traffic exposure due to the relatively rapid motorisation of transport in LICs, it is imperative to better understand the underlying mechanisms of road safety. This in turn will allow for planning cost-effective road safety improvement programs in a timely manner. With the general aim of improving road safety in LICs, this paper discusses the state of knowledge and proposes a number of future research directions developed from literature reviews and expert elicitation. Our study takes a holistic approach based on the Safe Systems framework and the framework for the UN Decade of Action for Road Safety. We focused mostly on examining the problem from traffic engineering and safety policy standpoints, but also touched upon other sectors, including public health and social sciences. We identified ten focus areas relating to (i) under-reporting; (ii) global best practices; (iii) vulnerable groups; (iv) disabilities; (v) road crash costing; (vi) vehicle safety; (vii) proactive approaches; (viii) data challenges; (ix) social/behavioural aspects; and (x) capacity building. Based on our findings, future research ought to focus on improvement of data systems, understanding the impact of and addressing non-fatal injuries, improving estimates on the economic burden, implementation research to scale up programs and transfer learnings, as well as capacity development. Our recommendations, which relate to both empirical and methodological frontiers, would lead to noteworthy improvements in the way road safety data collection and research is conducted in the context of LICs.

Estimated Prevalence of Opioid Use Disorder in Massachusetts, 2011-2015: A Capture-Recapture Analysis

OBJECTIVES

To estimate the annual prevalence of opioid use disorder (OUD) in Massachusetts from 2011 to 2015.

METHODS

We performed a multisample stratified capture-recapture analysis to estimate OUD prevalence in Massachusetts. Individuals identified from 6 administrative databases for 2011 to 2012 and 7 databases for 2013 to 2015 were linked at the individual level and included in the analysis. Individuals were stratified by age group, sex, and county of residence.

RESULTS

The OUD prevalence in Massachusetts among people aged 11 years or older was 2.72% in 2011 and 2.87% in 2012. Between 2013 and 2015, the prevalence increased from 3.87% to 4.60%. The greatest increase in prevalence was observed among those in the youngest age group (11-25 years), a 76% increase from 2011 to 2012 and a 42% increase from 2013 to 2015.

CONCLUSIONS

In Massachusetts, the OUD prevalence was 4.6% among people 11 years or older in 2015. The number of individuals with OUD is likely increasing, particularly among young people.

Estimating road traffic injuries in Jinja district, Uganda, using the capture-recapture method

Road traffic injuries (RTIs) are commonly under-reported in low-and-medium-income countries. This study aimed to estimate the number of RTIs and determine the magnitude of under-reporting by traffic police and hospital registries. A two-source capture-recapture method was applied to RTI data from police and hospital registries. Seven matching variables; sex of the injured, date, place, time, day of crash and road user type were used to get the matched cases. Police independently reported 46 RTIs and the hospitals reported 206 RTIs. Using the capture-recapture analysis, both sources estimated 313 RTIs (95% CI 273-343). The police registry captured 14.4% of the estimated number of RTIs and the hospitals captured 60.4%. The estimated number of RTIs was higher than reported by either the police or the hospitals alone. Neither the police nor the hospitals provided accurate data on RTIs, calling for the strengthening of both sources of data.

Record linkage for road traffic injuries in Ireland using police hospital and injury claims data

INTRODUCTION

The study of non-fatal road traffic injuries is growing in importance. Since there are rarely comprehensive injury datasets, it is necessary to combine different sources to obtain better estimates on the extent and nature of the problem. Record linkage is one such technique.

METHOD

In this study, anonymized datasets from three separate sources of injury data in Ireland: hospitals, police, and injury claims are linked using probabilistic and deterministic linkage techniques. A method is proposed that creates a 'best' set of linked records for analysis, useful when clerical review of undecided cases is not feasible.

RESULTS

The linkage of police and hospital datasets shows results that are similar to those found in other countries, with significant police understatement especially of cyclist and motorcyclist injuries. The addition of the third dataset identifies a large number of additional injuries and demonstrates the error of using only the two main sources for injury data.

PRACTICAL APPLICATION

The study also underlines the risk in relying on the Lincoln-Petersen capture-recapture estimator to provide an estimate of the total population concerned.

CONCLUSION

The data show that road traffic injuries are significantly more numerous than either police or hospital sources indicate. It is also argued that no single measure can fully capture the range of impacts that a serious injury entails.

Understanding traffic crash under-reporting: Linking police and medical records to individual and crash characteristics

OBJECTIVE

This study aligns to the body of research dedicated to estimating the underreporting of road crash injuries and adds the perspective of understanding individual and crash factors contributing to the decision to report a crash to the police, the hospital, or both.

METHOD

This study focuses on road crash injuries that occurred in the province of Funen, Denmark, between 2003 and 2007 and were registered in the police, the hospital, or both authorities. Underreporting rates are computed with the capture-recapture method, and the probability for road crash injuries in police records to appear in hospital records (and vice versa) is estimated with joint binary logit models.

RESULTS

The capture-recapture analysis shows high underreporting rates of road crash injuries in Denmark and the growth of underreporting not only with the decrease in injury severity but also with the involvement of cyclists (reporting rates of about 14% for serious injuries and 7% for slight injuries) and motorcyclists (reporting rates of about 35% for serious injuries and 10% for slight injuries). Model estimates show that the likelihood of appearing in both data sets is positively related to helmet and seat belt use, number of motor vehicles involved, alcohol involvement, higher speed limit, and females being injured.

CONCLUSIONS

This study adds significantly to the literature about underreporting by recognizing that understanding the heterogeneity in the reporting rate of road crashes may lead to devising policy measures aimed at increasing the reporting rate by targeting specific road user groups (e.g., males, young road users) or specific situational factors (e.g., slight injuries, arm injuries, leg injuries, weekend).

Disparities in road crash mortality among pedestrians using wheelchairs in the USA: results of a capture-recapture analysis

OBJECTIVE

This study aims to quantify and describe the burden of fatal pedestrian crashes among persons using wheelchairs in the USA from 2006 to 2012.

DESIGN

The occurrence of fatal pedestrian crashes among pedestrians using wheelchairs was assessed using two-source capture-recapture. Descriptive analysis of fatal crashes was conducted using customary approaches.

SETTING

Two registries were constructed, both of which likely undercounted fatalities among pedestrians who use wheelchairs. The first used data from the Fatality Analysis Reporting System, and the second used a LexisNexis news search.

OUTCOME MEASURES

Mortality rate (per 100 000 person-years) and crash-level, driver-level and pedestrian-level characteristics of fatal crashes.

RESULTS

This study found that, from 2006 to 2012, the mortality rate for pedestrians using wheelchairs was 2.07/100 000 person-years (95% CI 1.60 to 2.54), which was 36% higher than the overall population pedestrian mortality rate (p=0.02). Men's risk was over fivefold higher than women's risk (p<0.001). Compared to the overall population, persons aged 50-64 using wheelchairs had a 38% increased risk (p=0.04), and men who use wheelchairs aged 50-64 had a 75% increased risk over men of the same age in the overall population (p=0.006). Almost half (47.6%; 95% CI 42.8 to 52.5) of fatal crashes occurred in intersections and 38.7% (95% CI 32.0 to 45.0) of intersection crashes occurred at locations without traffic control devices. Among intersection crashes, 47.5% (95% CI 40.6 to 54.5) involved wheelchair users in a crosswalk; no crosswalk was available for 18.3% (95% CI 13.5 to 24.4). Driver failure to yield right-of-way was noted in 21.4% (95% CI 17.7 to 25.7) of crashes, and no crash avoidance manoeuvers were detected in 76.4% (95% CI 71.0 to 81.2).

CONCLUSIONS

Persons who use wheelchairs experience substantial pedestrian mortality disparities calling for behavioural and built environment interventions.

Road traffic deaths and injuries are under-reported in Ethiopia: a capture-recapture method

In low and middle income countries road traffic injuries are commonly under-reported. This problem is significantly higher among those less severely injured road users. The objective of this study was to determine the incidence and the level of ascertainment of road traffic injuries and deaths by traffic police and hospital registry. In this study two-sample capture-recapture method was applied using data from traffic police and hospital injury surveillance, through June 2012 to May 2013. The study was conducted on one of the busiest highways in Ethiopia, the Addis Ababa – Hawassa highway. Primary data were collected by accident investigators and hospital emergency nurses using a structured checklist. Four matching variables; name of the victim, sex, place and time of the accidents was used to get the matched cases. During the study period the police independently reported 224 deaths and 446 injuries/billion vehicle kilometer while hospitals reported 123 deaths and 1,046 injuries/billion vehicle kilometer. Both sources in common captured 73 deaths and 248 injuries/billion vehicle kilometer. Taking the two data sources into consideration, the capture-recapture model estimated the incidence of deaths and injuries ranged 368–390 and 1,869–1,895 per billion vehicle kilometer, respectively. The police source captured 57.4%–60.9% of deaths and 23.5%–23.9% of injuries while the hospital sources captured 31.5%–33.4% of deaths and 55.2%–56% of injuries. Deaths and injuries among females, younger age victims, cyclists/motorcyclists and pedestrians were under-reported by traffic police. In conclusion neither of the two sources independently provided accurate coverage of road traffic incident related deaths and injuries. Strengthening both systems is necessary to obtain accurate information on road accidents and human causalities.

Road traffic fatalities in Arkhangelsk, Russia in 2005-2010: reliability of police and healthcare data

PURPOSE

To estimate and compare reliability of traffic mortality data of the police and the healthcare sector in Arkhangelsk, Russia.

METHODS

The study matched traffic mortality data of the police and the regional healthcare statistics centre for the period from 2005 to 2010. Individual investigations of unmatched cases were performed, and the underlying causes of the non-matches were established. The obtained distribution of non-matches by causes served as basis for estimating the true numbers of traffic fatalities in the two sources, in appliance with corresponding fatality definitions and registration rules. A data accuracy index (DAI) was calculated for each source by using an adapted version of the formula for calculating accuracy of a diagnostic test. This was used as a measure for data reliability. Time trends in annual DAIs were estimated for each source by χ(2)-test for linear trend.

RESULTS

During the 6-year period, the police and the healthcare statistics centre registered 217 and 237 traffic fatalities in Arkhangelsk, respectively. Matching of data from the two sources resulted in 162 matched cases, 55 unmatched cases in the police data, and 75 unmatched cases in the healthcare data. More than a half (56%) of the non-matches were attributed to incompatibility of the definitions in the two data registration systems; 39% were attributed to failures in the healthcare data. Other non-matches were due to scarce identifying information (2%) or were not classifiable (2%). None of the non-matches were clearly attributable to failures in the police data. The 6-year DAI was 98% for the police data and 80% for the healthcare data. The DAI for the police data was stable over 2005-2010 (ranging from 96% to 100%). The DAI for the healthcare data increased from 66% in 2005 to 98% in 2010 (Ptrend<0.001).

CONCLUSION

The findings suggest that traffic mortality data of the police were more reliable, compared to the healthcare data. However, reliability of the healthcare data was improving during the study period.

A decline in the prevalence of injecting drug users in Estonia, 2005-2009

AIMS

Here we report a study aimed at estimating trends in the prevalence of injection drug use between 2005 and 2009 in Estonia.

BACKGROUND

Descriptions of behavioural epidemics have received little attention compared with infectious disease epidemics in Eastern Europe.

METHODS

The number of injection drug users (IDUs) aged 15-44 each year between 2005 and 2009 was estimated using capture-recapture methodology based on 4 data sources (2 treatment data bases: drug use and non-fatal overdose treatment; criminal justice (drug related offences) and mortality (injection drug use related deaths) data). Poisson log-linear regression models were applied to the matched data, with interactions between data sources fitted to replicate the dependencies between the data sources. Linear regression was used to estimate average change over time.

RESULTS

There were 24305, 12,292, 238, 545 records and 8100, 1655, 155, 545 individual IDUs identified in the four capture sources (police, drug treatment, overdose, and death registry, accordingly) over the period 2005-2009. The estimated prevalence of IDUs among the population aged 15-44 declined from 2.7% (1.8-7.9%) in 2005 to 2.0% (1.4-5.0%) in 2008, and 0.9% (0.7-1.7%) in 2009. Regression analysis indicated an average reduction of about 1600 injectors per year.

CONCLUSION

While the capture-recapture method has known limitations, the results are consistent with other data from Estonia. Identifying the drivers of change in the prevalence of injection drug use warrants further research.

Under-reporting of road traffic mortality in developing countries: application of a capture-recapture statistical model to refine mortality estimates

Road traffic injuries are a major cause of preventable death in sub-Saharan Africa. Accurate epidemiologic data are scarce and under-reporting from primary data sources is common. Our objectives were to estimate the incidence of road traffic deaths in Malawi using capture-recapture statistical analysis and determine what future efforts will best improve upon this estimate. Our capture-recapture model combined primary data from both police and hospital-based registries over a one year period (July 2008 to June 2009). The mortality incidences from the primary data sources were 0.075 and 0.051 deaths/1000 person-years, respectively. Using capture-recapture analysis, the combined incidence of road traffic deaths ranged 0.192-0.209 deaths/1000 person-years. Additionally, police data were more likely to include victims who were male, drivers or pedestrians, and victims from incidents with greater than one vehicle involved. We concluded that capture-recapture analysis is a good tool to estimate the incidence of road traffic deaths, and that capture-recapture analysis overcomes limitations of incomplete data sources. The World Health Organization estimated incidence of road traffic deaths for Malawi utilizing a binomial regression model and survey data and found a similar estimate despite strikingly different methods, suggesting both approaches are valid. Further research should seek to improve capture-recapture data through utilization of more than two data sources and improving accuracy of matches by minimizing missing data, application of geographic information systems, and use of names and civil registration numbers if available.

Measuring the population burden of fatal and nonfatal injury

The value of measuring the population burden of fatal and nonfatal injury is well established. Population health metrics are important for assessing health status and health-related quality of life after injury and for integrating mortality, disability, and quality-of-life consequences. A frequently used population health metric is the disability-adjusted life-year. This metric was launched in 1996 in the original Global Burden of Disease and Injury study and has been widely adopted by countries and health development agencies alike to identify the relative magnitude of different health problems. Apart from its obvious advantages and wide adherence, a number of challenges are encountered when the disability-adjusted life-year is applied to injuries. Validation of disability-adjusted life-year estimates for injury has been largely absent. This paper provides an overview of methods and existing knowledge regarding the population burden of injury measurement. The review of studies that measured burden of injury shows that estimates of the population burden remain uncertain because of a weak epidemiologic foundation; limited information on incidence, outcomes, and duration of disability; and a range of methodological problems, including definition and selection of incident and fatal cases, choices in selection of assessment instruments and timings of use for nonfatal injury outcomes, and the underlying concepts of valuation of disability. Recommendations are given for methodological refinements to improve the validity and comparability of future burden of injury studies.

Estimating the number of serious road injuries in the Netherlands

PURPOSE

This paper describes a new estimation method of the number of road injuries in The Netherlands.

METHODS

The bases for this method are the hospital inpatient registry and the police crash record database. Both databases contain errors and omissions. The police database in particular suffers from serious underreporting, and is also inaccurate in indicating injury severity. The hospital database is inaccurate in indicating that a patient was involved in a road crash. Nonetheless, in principle it contains all serious road injuries. After linking both databases an estimating method, inspired by capture-recapture, was used to estimate the number of road injuries. The differences in registration for transport mode, injury severity, and region of crash have been taken into account.

RESULTS

This leads to an estimation of the number of serious road injuries in the Netherlands in 1993-2008.

CONCLUSIONS

We found that 85% of the road injuries are recognizable as such in the hospital registry. The registration rate of the police registry is different for road injuries in crashes involving motorized vehicles (58% in 2008) and for road injuries in crashes not involving motorized vehicles (4% in 2008).

Linking emergency medical department and road traffic police casualty data: a tool in assessing the burden of injuries in less resourced countries

OBJECTIVE

The study aimed to (1) assess the magnitude of road traffic injuries in a country missing a formal linkage system of police with hospital data, (2) quantify the underreporting, and (3) produce a convenient algorithm exploring its constituent components.

METHODS

Linkage of disaggregate (individual) data collected by the road traffic police (RTP) with those by the Emergency Department Injury Surveillance System (EDISS) on the Greek island of Corfu and coded with different classification systems was carried out. The applied four-step methodology, also comprising the calculation of underreporting coefficients of the variation by basic demographic variables, mode of transport, and injury outcome, led to the identification of the overall underreporting from either registry.

RESULTS

RTP data captured 96.6% (coefficient: 1.035), whereas EDISS captured only 54.4% of total fatalities (overall concordance: 51.1%). On the contrary, EDISS captured 94.6% of nonfatal injuries, whereas RTP only captured 16% (coefficient: 6.238), resulting in a low overall concordance (10.6%). Considering severity of injury assessed by EDISS, by using the ISS as the gold standard, RTP data misclassified 20.3% of severe injuries as less severe, and a statistically significant difference in the underreporting by gender was also noted.

CONCLUSION

Relatively simple methodologies can provide essential coefficients to assess the actual numbers, severity, and components of road casualties by complementing routinely collected RTP with sentinel emergency department reporting systems.

Methodological issues in motorcycle injury epidemiology

Motorcycle riders are over 30 times more likely than car occupants to die in a traffic crash. While this fact is well known, specific issues of methodology in epidemiological motorcycle-injury research have been rarely researched. To facilitate more-valid research on motorcycle injuries, this article evaluates the current state of our knowledge on how we measure the population at risk of injury, completeness of case finding and identification, validity of crash/injury data sources, and completeness of information on important exposures such as alcohol consumption, helmet status, crash severity, and crash speeds, as well as problems of existing injury severity scales and statistical analyses for correlated injury data.

Estimating road traffic mortality more accurately: use of the capture-recapture method in the West Azarbaijan province of Iran

The study estimates the rate of fatal road traffic injuries (RTIs) by population and road-users group in one Iranian province. The capture - recapture method was employed, using both the death register and the forensic medicine register over one year. They recorded totals of 669 and 665 RTIs respectively, giving a non-overlapping number of 897 cases. An estimate of 1018 fatalities occurred, at rates of 34 per 100,000 of the population for all road users aggregated, 10 per 100,000 for pedestrians and 25 per 100,000 for other road users. Coverage was somewhat better for victims less than 15 years of age, and also for males. The method showed 121 under-reported cases in both sources; however, it can help Iranian policy-makers to produce a good estimation of fatal RTIs number each year, when following up current RTIs-prevention programmes. Yet, given that each registry operates separately, optimum coverage will only be obtained when both sources are integrated and work together.

Actual incidences of road casualties, and their injury severity, modelled from police and hospital data, France

BACKGROUND

Nation-wide road casualty figures usually come from police data. In France, as in many developed countries, the reporting of fatalities is almost complete but the reporting of non-fatal casualties is rather low. It is moreover strongly biased. Valid estimates are needed.

METHODS

Using the capture-recapture method on police data and on a road trauma registry covering a large county of 1.6 million inhabitants, we estimate police under-reporting correction factors that account for unregistered casualties. These correction factors are then applied to the nation-wide police data, with standardization on under-reporting bias factors.

RESULTS

In 2004, whereas the police report 108,727 non-fatally injured, the estimation yields 400,200. Over the 1996-2004 study period, the average annual estimated incidence is 871/100,000 for all injured (3.4 times the police incidence), 232/100,000 for hospitalized, 103/100,000 for seriously injured (2.2 times the police incidence) and 12.6/100,000 for casualties with long-term major impairment. The incidence of seriously injured (NISS 9+) is 11.3/100,000 for pedestrians, 9.5/100,000 for cyclists, 36.3/100,000 for motorized two-wheel users and 42.5/100,000 for car users.

CONCLUSIONS

The estimated incidences are much higher than the police-based ones. This changes the scale of the road injuries issue. The risk of suffering a major impairment from a road crash is equal to the risk of being killed. Motorized two-wheel users experience a large burden of traffic casualties, much larger than that indicated by police data. The approach used can be reproduced in other countries, if an additional medical registration exists.

Estimating crashes involving heavy vehicles in Western Australia, 1999-2000: a capture-recapture method

A two-sample exploratory study of police and hospital records was undertaken to estimate the number of fatalities and serious injuries for heavy vehicle drivers involved in a crash in Western Australia. The capture-recapture method was used to assess differences and similarities in characteristics of heavy vehicle drivers from both sources. Each heavy vehicle driver involved in a crash from the police report was matched against the heavy vehicle driver's hospitalisation record from the Hospital Morbidity Data System, with surname, initials, date of birth, gender, date of crash, road user type and vehicle type as matching fields. The estimated number of fatalities and serious injuries to heavy vehicle drivers from 1st July 1999 to 31st December 2000 was 5 and 59, respectively, which was 25 and 31% higher based on the capture-recapture methodology than the aggregated (non-overlapping) total officially reported to the police and hospitals. No significant age difference (p>0.05) was found for drivers involved in a heavy vehicle crash between the two sources (37 years versus 40 year of age). However, female heavy vehicle drivers were over-represented in the hospital records (11%) compared to the police records (1%). The capture-recapture approach is useful for evaluating the completeness of data sources and identifying biases within datasets. The underestimation of heavy vehicle drivers seriously injured and killed has important implications for heavy vehicle safety management and resource allocation in Western Australia.

Prevalence of autistic spectrum disorders in Lothian, Scotland: an estimate using the "capture-recapture" technique

AIMS

To determine the prevalence of autistic spectrum disorder in a geographically defined population for children receiving services and compare this to the estimated prevalence based on a two source “capture–recapture” technique previously employed in biological populations to give a “true” prevalence with full ascertainment.

METHODS

Information on gender, age, and postcode sector was determined from nine different datasets maintained for children with autistic spectrum disorder and point prevalence was calculated. Data from the diagnostic services and the Special Needs System were entered into the two source “capture–recapture” calculation.

RESULTS

Of a total population of 134 661 under 15 year olds resident in Lothian in southeast Scotland, 443 were known to autism services, with a point prevalence of 32.9 per 10 000 (95% CI 29.8 to 36.0). The estimated prevalence using a capture–recapture method was 44.2 (95% CI 39.5 to 48.9), which suggests that 74% of affected children were registered with services in some way. The age distribution was similar to that of the background population under the age of 12 years and there was no indication of a rising prevalence. The ratio of boys to girls was 7:1.

CONCLUSIONS

The prevalence of autistic spectrum disorder in a geographically based population employing two source capture–recapture analysis is comparable to that quoted for the best active ascertainment studies. This technique offers a tool for establishing the prevalence of this condition in health service populations to assist in planning clinical services.

Bayesian inference on the patient population size given list mismatches

In applying capture-recapture methods for closed populations to epidemiology, one needs to estimate the total number of people with a certain disease in a certain research area by using several lists with information of patients. Problems of lists error often arise due to mistyping or misinformation. Adopting the concept of tag-loss methodology in animal populations, Seber et al. (Biometrics 2000; 56:1227-1232) proposed solutions to a two-list problem. This article reports an interesting simulation study, where Bayesian point estimates based on improper constant and Jeffreys prior for unknown population size N could have smaller frequentist standard errors and MSEs compared to the estimates proposed in Seber et al. (2000). The Bayesian credible intervals based on the same priors also have super frequentist coverage probabilities while some of the frequentist confidence intervals procedures have drastically poor coverage. Seber's real data set on gestational diabetics is analysed with the proposed new methods.