The impact of income inequality in HIV testing among people who inject drugs in Tehran, Iran: A Blinder-Oaxaca decomposition

Abstract

ABSTRACTBackground: HIV testing plays an important role in any public health strategy for reducing HIV transmission and controlling HIV/AIDS among people who inject drugs (PWIDs). It is important to clarify whether HIV risk behaviors are explained by differences in the distributions of socio-demographic or socio-economic factors or some combination of both. In this study, we used a Blinder–Oaxaca decomposition for non-linear models to explore the relative contributions of variations in the distributions of socio-demographic versus their differential effects in producing economic inequalities in HIV testing in Tehran.Methods: This study is a cross-sectional survey of PWIDs in 2016 in Tehran. Participants were those who reported injecting drug use in the past month, were able to speak and comprehend Farsi enough to respond to survey questions, and provided informed consent to complete the interview. Participant income, which was used as a proxy measure of economic status, was the key explanatory variable. Economic status was measured by a composite index created by principal component analysis (PCA) using income information. we used the Blinder – Oaxaca (BO) method to decompose the economic inequality in HIV testing.Results: A total of 520 people were interviewed for the study. Data for these analyses are limited to the 500 who fully completed the questionnaire. The proportion of never- married was 40%, 73.3% had less than 6 years of schooling. Almost one quarter (24%) of participants had a monthly income of more than US$150 and almost half (42%) reported injecting illicit drugs more than 2 times per day. The most important factors in the explained component were knowledge of HIV (6.2%) and access to needle syringe programs (NSP) (4.2%). The lower level of knowledge of HIV in the low-economic group was the main factor responsible for the explained component.Conclusions: The results show that inequalities in HIV testing were primarily explained by the differential effects of access to harm reduction services and HIV knowledge for low and high economic status rather than by the differential distributions of these characteristics. Increasing access to harm reduction programs and increasing HIV knowledge are essential to efforts to eliminate HIV.