The psychosocial work environment and incident diabetes in Ontario, Canada.

BACKGROUND: Relatively few longitudinal studies have explored the relationship between psychosocial work conditions and diabetes incidence. Given the increasing global burden of diabetes this is an important area for public health research. AIMS: To examine the relationships between dimensions of the psychosocial work environment on the subsequent incidence of diabetes among men and women in Ontario, Canada over a 9 year period. METHODS: We used data from Ontario respondents (35 to 60 years of age) to the 2000-01 Canadian Community Health Survey linked to the Ontario Health Insurance Plan database for physician services and the Canadian Institute for Health Information Discharge Abstract Database for hospital admissions. Our sample of actively employed labour market participants with no previous diagnoses for diabetes was followed for a 9 year period to ascertain incident diabetes. RESULTS: There were 7443 participants. Low levels of job control were associated with an increased risk of diabetes among women, but not among men. Counter to our hypotheses high levels of social support were also associated with increased diabetes risk among women, but not among men. No relationship was found between any psychosocial work measure and risk of diabetes among men. CONCLUSIONS: Given the increasing prevalence of diabetes worldwide, job control could potentially be an import ant modifiable risk factor to reduce the incidence of diabetes among female, but not among male, workers. More research is needed to understand the pathways through which low social support may protect against the development of diabetes.

Disability management outcomes in the Ontario long-term care sector.

INTRODUCTION: Optimal disability management practices supporting early and safe return-to-work involve the workplace adoption of formal policies and procedures to ensure the quality of disability management outcomes. In the Canadian province of Ontario, there are approximately 60,000 health care workers in 600 licensed facilities providing long-term residential care to approximately 75,000 elderly residents. Workers in this sector are exposed to high biomechanical demands arising from care-giving tasks and have a substantial risk of work-related disability. Over the period 2000-2006, many long-term care facilities in Ontario adopted disability management practices that encourage modified work arrangements. The objective of this study was to describe differences in modified work arrangements and disability outcomes in long-term care facilities in Ontario. METHODS: Measures of disability episode outcomes are described for a representative sample of 32 Ontario long-term care facilities for two consecutive years 2005 and 2006. Data were obtained from a questionnaire survey of facilities, a survey of a representative sample of caregivers and administrative records from the provincial workers' compensation agency. RESULTS: A total of 28,747 days of disability attributed to work-related conditions were experienced by 3,271 full-time equivalent staff in 2005 (28,034 days in 2006). Average total disability days were 922 per 100 full-time equivalent staff in 2005 and 889 per 100 full-time equivalent staff in 2006. Disability compensation expenditures, measured as wage replacement benefits received by disabled workers, were estimated to be $72,332 per 100 full-time equivalent staff in 2005 and $64,619 per 100 full-time equivalent staff in 2006. On average, approximately 60% of all disability days were managed by modified duty arrangements and the proportion of total disability days managed by modified duty arrangements for each facility was correlated between the two observation years. CONCLUSIONS: Across facilities, there was no evidence that modified duty arrangements were associated with lower disability compensation expenditures and there was mixed evidence that modified duty was associated with a lower burden of disability. In this setting, disability days managed by modified duty arrangements were not accurately documented in worker's compensation claim records.

Comparing the risk of work-related injuries between immigrants to Canada and Canadian-born labour market participants.

OBJECTIVES: To examine the burden of work-related injuries among immigrants to Canada compared to Canadian-born labour force participants. METHODS: Using data from the 2003 and 2005 Canadian Community Health Surveys (n = 99,115), two nationally representative population samples, we examined the risk of self-reported, activity limiting work-related injuries among immigrants with varying time periods since arrival in Canada. Models were adjusted for hours of work in the last 12 months as well as various demographic and work-related variables. RESULTS: Immigrant men in their first 5 years in Canada reported lower rates of activity limiting injuries compared to Canadian-born respondents. Surprisingly, the percentage of injuries that required medical attention was much higher among recent immigrants compared to Canadian-born respondents, resulting in an increased risk of activity limiting injuries requiring medical attention among immigrant men compared to Canadian-born labour force participants. No excess risk was found among female immigrants compared to Canadian-born female labour market participants. CONCLUSIONS: Immigrant men in their first 5 years in Canada are at increased risk of work-related injuries that require medical attention. A similar risk is not present among immigrant women. Further, given differences in the number of activity limiting injuries requiring medical attention across immigrant groups, we believe this excess risk among immigrant men may be underestimated in the current data source. Future research should attempt to fully capture the barriers faced by immigrants in obtaining safe employment, the number of injuries that are sustained by immigrants while working, and the consequences of these injuries.

Examining the relationships between job control and health status: a path analysis approach.

OBJECTIVE: To examine the pathways through which job control affects health status; to examine if the effects of job control on health status are attenuated by including other measures associated with lower socioeconomic status, and to examine if the relationship between job control and health status is consistent across socioeconomic status groups. DESIGN: A prospective observational cohort study over eight years (1994-2002). PARTICIPANTS: 4886 Respondents aged 25-60 years, who were non-self-employed labour force participants, working more than 20 hours per week, without physical or mental limitations restricting the type or amount of work they could do at baseline. After longitudinal attrition, the remaining study sample was 3411 (87% of the original study sample who did not die or become pregnant during the survey period). MAIN RESULTS: Low job control in 1994 was associated with worse than expected self-rated health in 2002, both directly and indirectly via a lower physical activity level in 1996. Adjustment for other factors associated with low socioeconomic status did not attenuate these relationships to a large extent. No differences were found in the effects of job control on physical activity or health status between socioeconomic groups (high and low education and high and low household income). CONCLUSIONS: The inclusion of other factors associated with lower socioeconomic status did not attenuate the direct and indirect effects of job control on health status. The finding that low job control is associated with lower physical activity levels deserves further investigation, given the increasing concern about rising levels of obesity in the developed world.

Age-social stratification designs had a negligible impact on income-mortality associations.

OBJECTIVES: Age-social stratification has been used to offset socioeconomic status (SES) misclassification due to cohort effects. This study was to evaluate whether age-income stratification designs generate comparable income-mortality associations as those whose income rankings are based on absolute thresholds. STUDY DESIGN AND SETTING: Using self-reported income as our SES variable, and mortality as our outcome measure, the impact of age-social stratification was examined in two distinct cohorts: one with acute myocardial infarction (AMI) (n=3,138), and the second free of cardiovascular disease (n=15,115). Age-adjusted income-mortality associations were compared between age-social stratification techniques, which used "age-relative" income thresholds and "absolute" income thresholds whose ranks were independent of patient age. RESULTS: In both cohorts, crude mortality inversely correlated with age and income. Techniques using "age-relative" income thresholds yielded similar adjusted odds ratio for mortality as did those that used "absolute" income threshold methods (differences in adjusted odds ratios [+/-95% confidence interval (CI)] between "absolute" and "age-relative" classifications for highest vs. lowest income tertiles: -0.05 [-0.24, 0.12] among patients with AMI and 0.05 [-0.03, 0.13] among patients without cardiovascular disease). CONCLUSION: More complex designs incorporating age-social stratification techniques generate similar income-mortality associations as more simplified approaches, which classified SES using absolute income thresholds.

Healthcare use before and after a workplace injury in British Columbia, Canada.

OBJECTIVES: There is growing evidence that occupational injuries influence workers' emotional and physical wellbeing, extending healthcare use beyond what is covered by the Workers' Compensation Board (WCB). METHODS: The authors used an administrative database that links individual publicly funded healthcare and WCB data for the population of British Columbia (BC), Canada. They examined change in service use, relative to one year before the injury, for workers who required time off for their injuries (lost time = LT) and compared them to other injured workers (no lost time = NLT) and individuals in the population who were not injured (non-injured = NI). RESULTS: LT workers increased physician visits (22%), hospital days (50%), and mental healthcare use (43% physician visits; and 70% hospital days) five years after the injury, relative to the year before the injury, at a higher rate than the NI group. For the NLT workers, the level of increased use following the injury was between that of these two groups. These patterns persisted when adjusting for registration in the BC Medical Service Plan (MSP) and several workplace characteristics. CONCLUSIONS: Although the WCB system is the primary mechanism for processing claims and providing information about workplace injury, it is clear that the consequences of workplace injury extend beyond what is covered by the WCB into the publicly funded healthcare system.

Continuity of pediatric ambulatory care in a universally insured population.

OBJECTIVE: To describe the prevalence of continuity of care over a 5-year period in a complete cohort of urban children universally insured for medical care provided under fee-for-service reimbursement. METHOD: All children enrolled in the study were born to women living in metropolitan Winnipeg between July 1, 1987 and December 31, 1988 (N = 12,590). All ambulatory physician services for this group were enumerated from computerized administrative databases for the period from birth through 60 months. Continuity of care, defined as the proportion of total care provided by the most frequently seen physician or physician practice over time, was calculated for each child. Descriptive analyses include an examination of maternal and household characteristics associated with children receiving 80% or more of total ambulatory care from a single provider source. RESULTS: From birth to 24 months, 51% of children received at least 80% of ambulatory visits from a single provider practice. This proportion of the children declined to 28% at 25 through 60 months. Children living in low-income neighborhoods had poorer continuity profiles. Other household factors associated with poor continuity included young maternal age, single maternal marital status, residential mobility, and inadequate maternal use of prenatal medical care. Households affiliated with pediatric practices had better continuity profiles than households affiliated with general medical practices. CONCLUSION: Despite universal medical insurance, barriers to a longitudinally continuous relationship with a primary care provider remain in this setting. Although this study has emphasized the description of those barriers associated with household characteristics, there is evidence that factors related to the organization and delivery of medical care are also relevant.

Factors associated with nursing-home entry for elders in Manitoba, Canada.

BACKGROUND: As the population ages, a greater demand for long-term care services and, in particular, nursing homes is expected. Policy analysts continue to search for alternative, less costly forms of care for the elderly and have attempted to develop programs to delay or prevent nursing-home entry. Health care administrators require information for planning the future demand for nursing-home services. This study assesses the relative importance of predisposing, enabling, and need characteristics in predicting and understanding nursing-home entry. METHODS: Proportional hazard models, incorporating changes in needs over time, are used to estimate the hazard of nursing-home entry over a 5-year period, using health and sociodemographic characteristics of a representative sample of elderly residents from Manitoba, Canada. RESULTS: After age, need factors have the greatest impact on nursing-home entry. Specific medical conditions have at least as great a contribution as functional limitations. The presence of a spouse significantly reduces the hazard of entry for males only. CONCLUSIONS: The results suggest that the greatest gains in preventing or delaying nursing-home entry can be achieved through intervention programs targeted at specific medical conditions such as Alzheimer's disease, musculoskeletal disorders, and stroke.

Socioeconomic status, drug insurance benefits, and new prescriptions for inhaled corticosteroids in schoolchildren with asthma.

BACKGROUND: Low-income children with asthma are less likely to receive inhaled corticosteroid prescriptions that can prevent asthma morbidity. OBJECTIVE: To determine whether the receipt of inhaled corticosteroids in children with asthma is related to household socioeconomic status and type of drug insurance. DESIGN: Using population-based prescription and health care data from Manitoba, a cohort study of the determinants of receiving new prescriptions for inhaled corticosteroids was conducted in children treated with asthma drugs. PARTICIPANTS: School-aged children (n = 12 481) receiving asthma prescriptions from January 1995 to March 1996 but no inhaled corticosteroid prescriptions in the initial 6-month period. MAIN OUTCOME MEASURES: Household socioeconomic and drug insurance predictors of the probability of receiving a new inhaled corticosteroid prescription from July 1995 to March 1998, following adjustment for disease and health care utilization factors. RESULTS: In comparison with higher-income children insured through a provincial cost-sharing drug plan, the adjusted likelihood ratio for a new inhaled corticosteroid prescription was 0.88 (95% confidence interval, 0.80-0.97) in low-income children insured through the same drug plan and 0.82 (95% confidence interval, 0.76-0.88) in children receiving prescriptions at no charge through provincial income assistance or First Nations benefits programs (Winnipeg, Manitoba). CONCLUSION: Independent of asthma severity, type of drug insurance, or health care utilization patterns, low-income children with asthma are significantly less likely to receive inhaled corticosteroid prescriptions.

Gender differences in socioeconomic inequality in mortality.

OBJECTIVES: There is uncertainty about whether position in a socioeconomic hierarchy confers different mortality risks on men and women. The objective of this study was to conduct a systematic review of gender differences in socioeconomic inequality in risk of death. METHODS: This research systematically reviewed observational cohort studies describing all cause or cause specific mortality for populations aged 25-64 in developed countries. For inclusion in the review, mortality had to be reported stratified by gender and by one or more measures of socioeconomic status. For all eligible studies, five absolute and six relative measures of the socioeconomic inequality in mortality were computed for male and female populations separately. RESULTS: A total of 136 published papers were reviewed for eligibility, with 58 studies deemed eligible for inclusion. Of these eligible studies, 20 papers published data that permitted the computation of both absolute and relative measures of inequality. Absolute measures of socioeconomic mortality inequality for men and women generally agreed, with about 90% of studies indicating that male mortality was more unequal than female mortality across socioeconomic groups. In contrast, the pattern of relative inequality results across the 20 studies suggested that male and female socioeconomic inequality in mortality was equivalent. CONCLUSIONS: Inferences about gender differences in socioeconomic inequality in mortality are sensitive to the choice of inequality measure. Wider understanding of this methodological issue would improve the clarity of the reporting and synthesis of evidence on the magnitude of health inequalities in populations.

Age-specific education and income gradients in morbidity and mortality in a Canadian province.

While important age-related trends in the use of health care services over the past two decades in Canada have been well described, a comprehensive description of socioeconomic gradients in morbidity and mortality across age cohorts for a representative population has not been accomplished to date in Canada. The objective of this study was to describe age-specific socioeconomic differentials in mortality and morbidity for a representative sample of a single Canadian province. The study sample was formed from the linkage of individual respondent records in the 1986 census to vital statistics records and comprehensive records of health care utilization for a 5% sample of residents of the province of Manitoba. Using two measures of socioeconomic status derived from census responses, attained education and household income, individuals were stratified into age-specific quartile ranks. Based on diagnostic information contained on health care utilization records, the proportion of the sample in treatment during a 12-month observation period was calculated for 15 broadly defined categories of morbidity and tested for differences across socioeconomic quartiles. Mortality was inversely associated with both income and education quartile rank. In the analysis of morbidity, no association between socioeconomic status and treatment prevalence was observed in the majority, no association between socioeconomic status and treatment prevalence was observed in the majority of the 122 age- and disorder-specific strata tested. Of the observed associations, however, negative relationships were dominant, indicating a higher treatment prevalence among individuals of lower attained education or lower household income. Across the age course, negative relationships were most frequently present among young and middle aged adults, those aged 30-64, and were more consistently found for income than for education. The general findings of this study of a representative Canadian population support observations from other developed country settings that socioeconomic differences in relative rates of mortality and morbidity over the life course are greatest in the adult years.

Examining the associations between physical work demands and work injury rates between men and women in Ontario, 1990-2000.

AIMS: To describe the decline in injury rates between 1990 and 2000 within occupations stratified across three levels of physical demands and gender, adjusting for industry, in Canada's largest province. METHODS: Records of injury compensation claims were obtained from the Ontario Workplace Safety & Insurance Board. The population likely to be insured by the Ontario Workplace Safety & Insurance Board was estimated from Statistics Canada's Labour Force Survey. Injury rates were calculated by three broad levels of physical demands, separately for men and women. RESULTS: Injury rates decreased across each grouping of lower physical demands at work for both men and women, with the largest absolute differences in manual occupational groups (high physical demands). Occupations classified as manual (high physical demands) and mixed (moderate physical demands) showed larger differences in injury rates between genders than did non-manual (low physical demands), although the directions of these differences were not always consistent across different natures of injury classification. CONCLUSIONS: The absolute reduction in injury rates in Ontario between 1990 and 2000 was dominated by the reduction in injury rates for men and women in manual and mixed occupations. However, not all types of injury have declined to the same extent. A large proportion of differences in injury rates between men and women can be attributed to the differential labour force participation across occupations and industries, as well as the differential tasks within occupational groups.

Influence of magnetic resonance imaging on diagnosis and therapeutic intention.

RATIONALE AND OBJECTIVES: We assessed the contribution of magnetic resonance (MR) imaging to diagnostic and therapeutic decision making. METHODS: In a before-after observational study, we collected information from clinicians before and after patients were given MR examinations. We studied 406 cases selected from consecutive referrals to a single MR imaging facility in Manitoba between November 1, 1991, and October 30, 1992, for diagnosis of suspected brain, spinal column, or large-joint disorder. We examined changes in diagnoses, changes in clinician diagnostic confidence, and changes in therapeutic intentions after MR examinations. RESULTS: Overall, MR imaging findings contributed to a change in referring physicians' diagnoses or diagnostic confidence in 76% of the cases. Referring physicians reported a change in provisional diagnosis in 42% of the cases. In 67% of these cases, the referring physician's provisional diagnosis was ruled out by normal examination findings; in the remaining 33% of the cases, an alternate diagnosis was offered by the consulting radiologist. In the 58% of the cases in which the provisional diagnosis was not altered by MR imaging findings, clinical confidence in the provisional diagnosis increased in 46% of the cases and decreased in 12% of the cases. Management plans were reported to be altered in 54% of the cases; in 24% of the cases, therapeutic intentions changed from lower to higher levels of intervention. CONCLUSION: Although MR imaging had a substantial influence on clinicians' decisions concerning diagnoses, the influence of MR imaging findings on therapeutic decision making, and therefore on patients' health status, was more moderate.

Epidemiology of incident spinal fracture in a complete population.

STUDY DESIGN: Cross-section observational study of incident spinal fractures using an administrative data-base. OBJECTIVES: To identify and define all patients who have spinal fractures within a complete population. SUMMARY OF BACKGROUND DATA: The true incidence of spinal column and cord injury is not known. Previous studies have been institutional or practice based. Accurate information concerning the magnitude of the spinal injury population and their characteristics may provide more rational basis for public health decision making and resource allocation. METHODS: The study dates were April 1, 1981 to March 31, 1984. Using the Manitoba Health Services Insurance Plan database, all patients with ICD-9-CM coding of 805.x and 806.x (spinal column fracture with and without spinal cord injury) were identified. Incidence rates, age and gender distribution, and ambulatory and hospital contracts were identified. Hospital discharge abstracts were used to classify mechanisms of injury, associated injuries, and length of stay. RESULT: The annual incidence rate of spinal fracture was 64 per 100,000. Two thousand sixty-three patients were identified, with 944 being admitted to the hospital. There were two peaks of incidence occurring in young men and elderly women. Of the hospitalized patients, 182 had cervical injury, 286 had thoracic fracture, and 403 had injury in the lumbosacral spine Associated injuries occurred in 38% of hospitalized patients. Length of stay was an average of 38.5 days. Overall mortality was 41%. Neurologic injury occurred in 122 patients. CONCLUSIONS: Ambulatory care of spine injuries is more common than hospital care. Two peaks of incidence occur-in young men and elderly women. Future decisions for research, public health policy, and resource allocation can be based on these data.

Widening regional inequality in premature mortality rates in Manitoba.

OBJECTIVE: To describe regional trends in premature mortality in Manitoba. DESIGN: Comparison of all-cause and cause-specific mortality of persons less than age 75 in 11 Regional Health Authority populations over two time periods: 1985-89 and 1990-94. RESULTS: The provincial premature mortality rate declined over the two time periods (4.00/1,000 to 3.72/1,000). Declines were also observed in 9 of 11 regional populations. Premature mortality increased, however, in the 2 regional populations with the highest mortality rates in the first observation period. CONCLUSION: Declining premature mortality in low mortality populations and rising premature mortality in high mortality populations has resulted in a widening of regional mortality rates in Manitoba. Recent policy initiatives in many provinces, including the devolution of authority for the management and delivery of health services and the implementation of population need-based funding formulas to share health care resources among regional health authorities, if implemented, have the potential to partially mitigate the processes producing these widening regional health inequalities.

Work-related population health indicators.

OBJECTIVE: To provide evidence-based recommendations for work-related population health indicators. METHODS: Drawing on a framework of work-related experiences, we systematically reviewed studies that assess the association between these experiences and health and reviewed related measures at the population level that could be used as indicators. RESULTS: We recommend (and grade the strength of evidence supporting our recommendation for) the following indicators for which data are already routinely collected: unemployment rate (strong), long-term unemployment rate (limited), and permanent lay-off rate (limited). As well, we recommend and grade our support for the following new indicators: insecurity associated with pending job loss (limited), with possible major organizational change (limited), and with actual major organizational change (limited); and job strain (medium). CONCLUSION: These evidence-based indicators can be used to monitor work-related determinants of health and thus to inform the conceptualization, development, and evaluation of policies and programs related to these determinants.

Assessing ecologic proxies for household income: a comparison of household and neighbourhood level income measures in the study of population health status.

This paper examines the validity of using ecologic measures of socioeconomic status as proxies for individual-level measures in the study of population health. Based on a representative 5% sample of households in a Canadian province, the study integrated three sources of information: administrative records of individual health care utilization, records of deaths and 1986 census records which contained information on household income and average neighbourhood income. Thirteen measures of health status were developed from these sources of information. The hypothesis that risk estimates derived from ecologic income measures will be attenuated relative to estimates obtained from household income was not supported. These results provide evidence for the use of ecologic-level measures of income in studies which do not have access to individual-level income measures.

Childhood and early adult predictors of risk of incident back pain: Ontario Child Health Study 2001 follow-up.

Musculoskeletal disorders of the back and spine are a leading cause of disability in working-age populations. There is limited information on the potential consequences of childhood socioeconomic and health status on the risk of incident back pain in early adulthood. The authors describe factors associated with having had a first episode of back pain during the past year in the Ontario Child Health Study, a prospective cohort study of children who were aged 4-16 years at the time of enrollment in 1983 and were resurveyed in 2001. Respondents reporting a first episode of back pain (n=143) were compared with respondents who had never experienced back pain (n=896). The annual incidence of a first episode of back pain in this sample of young adults was 74.7/1,000. Following adjustment for age, sex, childhood conditions, childhood health status, and measures of early adult health, behavior, socioeconomic status, and work environment, the risk of incident back pain was associated with both low (odds ratio (OR)=1.86, 95% confidence interval (CI): 1.14, 3.03) and moderate/high (OR=1.85, 95% CI: 1.07, 3.02) levels of psychological distress, current heavy smoking (OR=1.85, 95% CI: 1.10, 3.10), lower levels of parental education in childhood (OR=1.72, 95% CI: 1.06, 2.80), and emotional or behavioral disorders in childhood (OR=1.87, 95% CI: 1.02, 3.41). The associations of low childhood socioeconomic status and childhood emotional and behavioral disorders with risk of incident back pain in early adulthood are important findings with implications for better understanding the etiology of soft-tissue disorders.

The relationship of prenatal care and pregnancy complications to birthweight in Winnipeg, Canada.

OBJECTIVES: Prenatal care is commonly understood to have a beneficial impact on birthweight. This study describes socioeconomic differences in utilization of prenatal medical care and birthweight in a population with universal health insurance. METHODS: Measures of prenatal care utilization, incidence of pregnancy complications, and birthweight were obtained from physician reimbursement claims and hospital separation abstracts for 12,646 pregnant women. Maternal socioeconomic status was derived from small-area census data. RESULTS: Infants born to women in the poorest income quintile had lower birthweights than infants born to wealthier women. Much of the difference was associated with a higher prevalence of complications, smoking, unmarried status, and inadequate prenatal care among low-income women. The difference in birthweight between adequate and less than adequate care groups was small, and the benefit associated with prenatal care was no greater among women with pregnancy complications. CONCLUSIONS: The lower utilization of prenatal care by poorer women accounted for a small proportion of the difference in birthweight. Socioeconomic differences in birthweight are primarily attributable to factors not directly influenced by early prenatal medical care.

Validation of an electronic, population-based prescription database.

BACKGROUND: The Drug Programs Information Network (DPIN), Manitoba's (Canada) new electronic prescription database, is a valuable data source for pharmacoepidemiologic research. Pharmacies are required to submit to the DPIN all prescriptions for Pharmacare, the province's drug insurance plan, but submission of prescriptions for social assistance recipients and treaty status Indians is discretionary. OBJECTIVE: The completeness of the DPIN prescription database was assessed to determine whether treaty status Indians and social assistance recipients were underrepresented. DESIGN: Prescriptions dispensed during March 13-17, 1995, in a stratified sample of Manitoba pharmacies were linked to DPIN by prescription number to determine the proportions submitted for Indian Affairs, Social Services, and Pharmacare recipients. Pharmacare records in the DPIN were compared with original pharmacy records to evaluate data accuracy. RESULTS: Of 2196 Indian Affairs and 1879 Social Services prescriptions dispensed in 58 pharmacies, a corresponding prescription was found in the DPIN for 79.7% (98% CI 78.0% to 81.4%) and 90.1% (98% CI 88.8% to 91.4%) of prescriptions, respectively. These proportions were significantly lower than the estimated proportion of Pharmacare prescriptions submitted (93%, 98% CI 92.4% to 93.6%). Ninety-two percent of 8012 DPIN Pharmacare prescriptions matched the original prescription on the drug name, quantity, and days' supply. CONCLUSIONS: This study established that the DPIN is a valid and reliable data source for studying prescription use among the majority of Manitoban residents. However, the DPIN database has differential validity and underrepresents prescriptions dispensed for the aboriginal population.