Objective: To examine whether individual characteristics were associated with differential use of viral load testing when testing is available without charge to all HIV-positive patients with provincial health insurance.
Methods: Individuals enrolled in the HIV Ontario Observational Database with complete medication records and health insurance numbers for linkage were studied. Generalized estimating equation regression models were used to examine the relationship between time-varying covariates such as plasma viral load levels, CD4 counts, and antiretroviral regimen characteristics and the number of days between viral load tests and the occurrence of an interval of >or=6 or 9 months between tests.
Results: A total of 1032 individuals were included in the analysis with a median follow-up of 4.6 years and a median of 18 viral load tests. In multivariate analyses, clinically important gaps in viral load testing were more likely among injection drug users (odds ratio [OR]=1.86, P<0.0001), in more recent years (P<0.01) and for individuals not using antiretrovirals (OR=1.70, P<0.0001) and less likely among individuals using >4 antiretrovirals (OR=0.62, P<0.0001). Results were similar when the outcome was the number of days between tests.
Conclusions: Injection drug users, younger individuals, and residents of Toronto used fewer viral load tests than other individuals, even when financial barriers to testing were removed.