Abstract:

Background: The intent of ART is to attain as sustained adequate virological suppression to allow a significant immunological recovery. This is achieved through prolonged use of ARV at therapeutic range. Subtherapeutic level would cause inadequate virological suppression and ultimately poor immunological outcome. Subtherapeutic drug levels are a significant cause of treatment failure among adult patients on ARV but the magnitude of this problem is not known in our setting. Therefore this study was conducted to determine the proportion of Subtherapeutic ARV drug levels and their associated factors among adult HIV patients attending Care and Treatment Centre at Bugando Medical Centre.

Materials and Methods: A cross sectional hospital based study was conducted among adult HIV patients on ARV with immunological failure and those with TB co treatment. Patients were serially enrolled through routine CTC activities until the sample size was reached. All the information about demographic, clinical and adherence level characteristics, viral load, CD4 and ARV serum levels of these patients were recorded and analyzed using STATA 11 software.

Results: During the study period a total of 274 adult HIV positive patients on ART were enrolled where by 156 (56.9%) had immunological failure and 118 (43.1%) were on TB co treatment. The time on ART was between one to 100 months. Most patients 177 (64.6%) were on EFV based regimen and a total of 75/274 (27.4%) were found to have Subtherapeutic ARV serum levels. Among patients with immunological failure more than 48% had no evidence of virological failure. By TDM 31.4% were found to have Subtherapeutic ARV levels and this was strongly predicted by baseline CD4 less than 200cell/ml (OR= 2.4, 95%CI = 1.2-5.2, p=0.001), adherence rare less than 95% (OR=19.3, 95%CI=6.1-60.7, p<0.0001), and a viral load of more than 400c/mcl (OR=2.5, 95%CI=1.2-5.1, p=0.008). Among patients with TB co treatment 22% had Subtherapeutic ARV levels and this had strong associations with adherence level of less than 95% (OR=4.5, 95%CI=1.7-11.8, p=0.003), virological failure (OR=2.9, 95%CI 1.1-7.9, p=0.032), and being on a NVP based regime female gender (OR=2.9, 95%CI 0.13-93, p=0.035), (OR=13.4, CI=1.3-136, p=0.028.

Conclusion: A significant number of adult HIV patients attending CTC in Tanzania with immunological failure and that co treated with antiTB have Subtherapeutic ARV drug levels and TDM could assist identifying these patients early and making timely correction to avoid immediate virological failure and a long term poor immunological outcome.

Recommendations: We should counsel patients to maximize adherence level to ensure compliance to medication among our patient on antiretroviral therapy. We should maximize availability and sustainability of viral load measurement facilities. To identify potential with poor virological response in whom TDM might be useful.