Cohort profile: Seek and treat for the optimal prevention of HIV/AIDS in British Columbia (STOP HIV/AIDS BC)

Abstract

The Seek and Treat for Optimal Prevention of HIV/AIDS (STOP HIV/AIDS) cohort is a census of all identified HIV-positive individuals in the province of British Columbia. It was formed through the linkage of nine provincial treatment, surveillance and administrative databases. This open cohort allows for bidirectional analyses from 1996 onward and is refreshed annually. Extensive data collection for cohort members includes demographic information, detailed clinical and laboratory data, complete prescription drug use including antiretroviral agents, and information on health service utilization encompassing inpatient and outpatient care, addictions treatment and palliative care. This cohort provides an unprecedented opportunity to evaluate, over an extended time period, patterns and determinants of key outcomes including engagement in the cascade of HIV care from diagnosis to treatment to viral suppression as well as monitoring trends in medical costs, health outcomes and other key healthcare delivery indicators at a population level with wide-ranging, high-quality data. The overall purpose of these activities is to enable the development and implementation of strategically targeted interventions to improve access to testing, care and treatment for all HIV-positive individuals living in British Columbia.

Figure 1.

Loss to follow-up and mortality among STOP HIV/AIDS cohort participants in British Columbia from 1996 to 2008 (N = 12 349), defined as those without health service utilization recorded in any of the nine databases used to create the STOP cohort.

Figure 2.

Cohort membership: 1996 to 2009. HIV-positive: based on annual HIV prevalence estimates reported by the Public Health Agency of Canada. Diagnosed: defined as the first instance of a confirmed HIV-positive test, detectable plasma viral load (pVL), HIV-related MSP billing or hospitalization, reported AIDS-defining illness or antiretroviral treatment. Linked: among diagnosed cases, defined as the first instance of HIV-related service following HIV diagnosis among those with confirmed HIV test and the first instance of HIV-related service ≥30 days following HIV diagnosis among those with no confirmed HIV test. Retained: among individuals linked to HIV care, defined as three HIV-related services provided on distinct dates, within the calendar year or access to antiretroviral treatment. Need antiretroviral therapy (ART): among individuals with any record of CD4 and/or pVL, individuals qualify if they have reached 2009 IAS-USA initiation criteria, CD4 ≤350 or AIDS-defining illness. Accessing ART: among those linked to HIV care, defined as receiving an antiretroviral drug dispensation at least once in the calendar year. Adherent: among individuals on antiretroviral therapy, defined as having at least 80% adherence in 2009, or from the point of antiretroviral initiation that year. Suppressed: no detectable pVL in two consecutive measurements during 2009.

Figure 3.

Age pyramid stratified by sex for STOP HIV/AIDS cohort participants alive in 2009.

Figure 4.

Identified HIV-positive individuals and number on ART in British Columbia from 1996-2009, i.e. positive HIV test on record or with healthcare resource utilization patterns consistent with HIV.

Figure 5.

Spectrum of engagement in care for STOP HIV/AIDS cohort participants in British Columbia in 2009.