Hepatitis C Virus (HCV) is an infection that can have grave consequences when left untreated. Hepatitis C can be easily eradicated with direct acting antiviral therapy. People who inject drugs (PWID) and inmates are among those with the highest incidence of HCV. However, cure rates among this population remains low. This is, in part, related to an interruption in the HCV care cascade such that only 30% of PWID are linked to care and only 8% of those receive treatment. Inadequate screening and failure to be linked to HCV care remain the largest impediments to treatment success. There is limited research on barriers and facilitators to primary care, where screening may take place, and linkage to HCV care among PWID. Few studies have evaluated vulnerable populations such as those living in rural communities or inmates. The purpose of this dissertation was to develop a broader understanding of barriers and facilitators to healthcare utilization among PWID at the primary care and specialist levels (linkage to care). Three manuscripts addressed important gaps in knowledge. The first was a review of the literature to describe the state of science on linkage to care among PWID. All but one reviewed study recruited from countries with universal healthcare, urban areas, and opioid substitution facilities. The review of the literature revealed that little is known about the barriers/facilitators to linkage to HCV care faced by rural-dwelling PWID from countries without universal healthcare. The second manuscript is a study to determine whether predictors of linkage to care identified in urban-dwelling PWID from countries with universal healthcare predicted seeking HCV care among PWID living in rural Appalachia. Data were obtained from a subsample of 63 HCV positive PWID who recently used opioids, were between the ages of 18-35 years, and lived in one of five rural counties in Kentucky. Logistic regression revealed that recent injection drug use was the only predictor of seeking HCV care. However, remote use of opioid substitution therapy and no transportation issues approached clinical significance. Although not evaluated in our second manuscript, seeing a primary care provider (PCP) is associated with an increased likelihood of being linked to care and higher rates of screening/diagnosis. Among rural dwelling PWID, there are subpopulations that may face unique barriers to linkage to care. One sub-population that may be particularly vulnerable are female PWID who are incarcerated. Therefore, the purpose of the third study was to determine predictors of primary care use using data from 302 female inmates from rural Appalachia with a history of injecting drugs. Age, insurance issues, and health problems that interfere with responsibilities were predictors of PCP use. In this dissertation, I have addressed important gaps in the literature by determining barriers and facilitators to seeking HCV care and primary care use among PWID from rural Kentucky. Additional studies are needed using a larger sample of rural PWID to confirm our findings. In addition, further studies should evaluate system and provider level barriers to linkage to care and PCP use among rural PWID.

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This thesis evaluates the cost-effectiveness of eight policies expanding human immunodeficiency virus (HIV) testing in South Africa. All policies entail provider-initiated test offers for primary healthcare users and one of two options across three policy components: (i) consent method, opt-in or opt-out; (ii) test protocol, rapid only or rapid plus acute infection testing; and (iii) linkage-to-care, standard or enhanced. This thesis highlights four methodological issues. First is the challenge of conducting a population-level analysis, projecting the cost-effectiveness of expanded testing for each member of South Africa’s adult African population. To this end, I conducted a retrospective, descriptive study to measure current population-level testing rates and epidemic descriptors in an African community near Cape Town, South Africa. Second, the effects of testing expansion on current testing uptake were estimated by distinguishing testing in the study community likely to cease after testing expansion (baseline testing) from that likely to continue (background testing). Third, because testing alone is an outcome of less interest than health benefits following treatment, study community linkage-to-care probabilities were estimated and models utilized to estimate the efficacy of treatment. Fourth, the methods to convert the study community testing data into inputs for these models’ parameters are outlined. The enhanced linkage-to-care policies proved the most cost-effective, with opt-in testing and a rapid-only test protocol the least expensive cost-effective option at $848 per life year gained (LYG). Adding an opt-out consent method or acute infection test protocol to this policy increased the LYGs, but at higher cost-effectiveness ratios.