Identification of people with low prevalence diseases in administrative healthcare records: A case study of HIV in British Columbia, Canada.

INTRODUCTION: Case-finding algorithms can be applied to administrative healthcare records to identify people with diseases, including people with HIV (PWH). When supplementing an existing registry of a low prevalence disease, near-perfect specificity helps minimize impacts of adding in algorithm-identified false positive cases. We evaluated the performance of algorithms applied to healthcare records to supplement an HIV registry in British Columbia (BC), Canada. METHODS: We applied algorithms based on HIV-related diagnostic codes to healthcare practitioner and hospitalization records. We evaluated 28 algorithms in a validation sub-sample of 7,124 persons with positive HIV tests (2,817 with a prior negative test) from the STOP HIV/AIDS data linkage-a linkage of healthcare, clinical, and HIV test records for PWH in BC, resembling a disease registry (1996-2020). Algorithms were primarily assessed based on their specificity-derived from this validation sub-sample-and their impact on the estimate of the total number of PWH in BC as of 2020. RESULTS: In the validation sub-sample, median age at positive HIV test was 37 years (Q1: 30, Q3: 46), 80.1% were men, and 48.9% resided in the Vancouver Coastal Health Authority. For all algorithms, specificity exceeded 97% and sensitivity ranged from 81% to 95%. To supplement the HIV registry, we selected an algorithm with 99.89% (95% CI: 99.76% - 100.00%) specificity and 82.21% (95% CI: 81.26% - 83.16%) sensitivity, requiring five HIV-related healthcare practitioner encounters or two HIV-related hospitalizations within a 12-month window, or one hospitalization with HIV as the most responsible diagnosis. Upon adding PWH identified by this highly-specific algorithm to the registry, 8,774 PWH were present in BC as of March 2020, of whom 333 (3.8%) were algorithm-identified. DISCUSSION: In the context of an existing low prevalence disease registry, the results of our validation study demonstrate the value of highly-specific case-finding algorithms applied to administrative healthcare records to enhance our ability to estimate the number of PWH living in BC.

Factors behind HIV testing practices among Canadian Aboriginal peoples living off-reserve.

The objective of this study was to examine factors associated with HIV testing among Aboriginal peoples in Canada who live off-reserve. Data were drawn for individuals aged 15-44 from the Aboriginal Peoples Survey (2001), which represents a weighed sample of 520,493 Aboriginal men and women living off-reserve. Bivariable analysis and logistic regression were used to identify factors associated with individuals who had received an HIV test within the past year. In adjusted multivariable analysis, female gender, younger age, unemployment, contact with a family doctor or traditional healer within the past year, and "good" or "fair/poor" self-rated health increased the odds of HIV testing. Completion of high-school education, rural residency, and less frequent alcohol and cigarette consumption decreased the odds of HIV testing. A number of differences emerged when the sample was analyzed by gender, most notably females who self-reported "good" or "fair/poor" health status were more likely to have had an HIV test, yet males with comparable health status were less likely to have had an HIV test. Additionally, frequent alcohol consumption and less than high-school education was associated with an increased odds of HIV testing among males, but not females. Furthermore, while younger age was associated with an increased odds of having an HIV test in the overall model, this was particularly relevant for females aged 15-24. These outcomes provide evidence of the need for improved HIV testing strategies to reach greater numbers of Aboriginal peoples living off-reserve. They also echo the long-standing call for culturally appropriate HIV-related programming while drawing new attention to the importance of gender and age, two factors that are often generalized under the rubric of culturally relevant or appropriate program development.