Introduction: Virologic failure defined as viral load above 1000 copies/mL based on two consecutive viral load measurements in 3 months apart, with adherence support following the first viral load test is .The primary goal of ART is to reduce the viral load in HIV infected patients with the purpose of promoting quality of life, as well as reduction of HIV-related morbidity and mortality. High rate of virologic failure was reported in Wag Himera Zone, Northwest Ethiopia in viral load assessment conducted among HIV-infected patients on HAART in Amhara region. However, there is limited evidence on the determinants of virological failure in the study area.

Objective: The aim of this study was to identify the determinants of virological failure among HIV-infected patients on Antiretroviral Therapy in wag Himera zone, North Ethiopia, 2018

Methods: An institutional-based unmatched case control study was conducted from June 8 to July 30, 2018. Cases were HIV patients on ART who had already experienced virological failure; controls were those without virological failure. Data was extracted from 90 cases and 181controls through chart review using pretested and structured checklist. The data was entered using Epi info version 7, and exported to SPSS version 20 for analysis. A multivariate logistic regression analysis was carried out to identify factors associated with virological failure, and variables with a p-value <0.05 were considered statistically significant.

Results: In this study patients who had shown poor adherence to HAART (AOR=9.34, 95% CI: 4.49,19.46), had taken HAART for longer than five years (AOR=2.47, 95% CI: 1.17, 6.04), had drug toxicity (AOR =5.81 95% CI: 2.51, 13.68), age of patient (AOR= 1.05 95% CI: 1.01,1.09),peak CD4 count <200 cells/mm³(AOR=5.18, 95% CI: 1.56,17.22) were factors which shown higher odds of virologic failure.

Conclusion and recommendation: This study showed that poor adherence to treatment, longer duration on HAART, experiencing drug toxicity ,older age of patients and peak CD4 < 200 cell/mm³ are factors which increases the risk of Virologic failure.  Therefore identifying the cause of non-adherence and increasing adherence to HAART would help to suppress viral replication. Special attention should be given for patients with history of drug toxicity, stay longer on HAART, and low peak CD4 count.

KEY WORDS: Virologic failure, Determinants, ART, Wag Himera