Thesis (MMed) -- Stellenbosch University, 2010. / Bibliography / Objective: The objective of this retrospective cohort study is to assess whether demographic and anthropometric parameters, laboratory tests, co-morbidity, co-infection, treatment regimen, IRIS and adherence to treatment predict the expected response to HAART and differences if any, in the pattern of response as measured by CD4 count, weight gain and haemoglobin levels in two cohorts of patients in Roma, The Kingdom of Lesotho. Method: Data were collected randomly from a computerised database of the Antiretroviral Centre of the hospital and two cohorts of 151 subjects in each of the two arms of the study were identified from hospital records from January 2008. Each of these subjects was followed up over a period of 12 months with data obtained for at least 2 visits within the 12 month span. Data were obtained at baseline, 3 months and also at 6 and 12 months marks. Data on characteristics were compared between the two arms. Variables that may be potential confounders were identified and univariate and multivariate logistic regression analyses were carried out to establish differences independent of confounding factors for the combined endpoints as well as for each endpoint separately. Results: In all 302 patients had their records analysed and comparison of clinical and immunological response patterns in patients taking AZT and TDF-containing ART regimens and the possible prediction of which the regimen would be better and within which population. Despite the perceived mismatch between two NRTIs it can be concluded from the results of this study that, overall, the inclusion of AZT in treatment regimen showed a modest protective effect over the TDF counterpart as measured by the endpoints of the discriminative powers of the Receiver Operating Curves of the explanatory variables being 66% , 77% and 66% for CD4, Haemoglobin and Weight respectively, and 63%, 70% and 65% for the same variables in the AZT and TDF arms of the study respectively. Conclusion: In a population of HIV patients on treatment in resource-limited settings AZT-containing regimens appear to show a slight improvement over the TDF-containing ones.