How does hard-to-reach status affect antiretroviral therapy adherence in the HIV-infected population? Results from a meta-analysis of observational studies

BACKGROUND: Socially disadvantaged groups, such as drug users, sex workers and homeless individuals, are labelled as “hard-to-reach” (HTR) in public health and medical research. HIV disproportionately impacts these populations, but data on how the HTR status could affect antiretroviral therapy (ART) adherence among HIV-positive people are limited and have not been previously synthesized in a systematic manner. We performed a meta-analysis to explore the association between HTR status and optimal antiretroviral therapy adherence in the HIV-infected population to provide evidence and recommendations regarding ART adherence improvement and HIV infection control and prevention among HTR people. METHODS: The PubMed, EMBASE, and Cochrance Library databases and the bibliographies of relevant studies were systematically searched up to December 2018. Full-text studies published in English were included, and no geographic or race restrictions were applied. Studies that quantitatively assessed the association between HTR status and optimal ART adherence among HIV-infected populations with a status of homelessness, sex work, or drug use were eligible for inclusion. We estimated the pooled odds ratios (ORs) of HTR characteristics related to ART adherence from each eligible study using a random effects model. The sensitivity, heterogeneity and publication bias were assessed. RESULTS: Our search identified 593 articles, of which 29 studies were eligible and included in this meta-analysis. The studies were carried out between 1993 and 2017 and reported between 1999 and 2018. The results showed that HTR status resulted in a 45% reduction in the odds of achieving optimal ART adherence compared to odds in the general population (OR = 0.55, 95% confidential intervals (CIs) 0.49–0.62), and this significant inverse association was consistently found regardless of study design, exposure measurement, adherence cut-off points, etc. Subgroup analyses revealed that the HTRs tend to be suboptimal adhering during a longer observational period. CONCLUSIONS: HIV treatment adherence is extremely negatively affected by HTR status. It is crucial to develop appropriate interventions to improve ART adherence and health outcomes among HTR people who are HIV-infected. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (10.1186/s12889-019-7135-0) contains supplementary material, which is available to authorized users.