Introduction:
Resistance to antiretroviral medications poses challenges for the successful treatment of human immunodeficiency virus 1 (HIV-1) infection. Genotypic antiretroviral testing provides guidance for selecting the proper treatment regimens. We studied the prevalence of HIV-1 resistance mutations in a population of U.S. veterans.

Material and methods:
A retrospective chart review was performed on 230 patients who presented to an outpatient infectious diseases clinic for routine HIV-1 care between 2000 and 2016. Charts were reviewed to extract available information on genotype test results and relevant demographic data.

Results:
Of the 230 patients, 98 had available genotype tests. A total of 113 genotype tests were collected for analysis. Fifty-three genotypes were baseline tests; 60 were obtained following virologic failure. The median age of the study group was 58 years. Ninety-four of the 98 subjects were men. Risk factors for HIV-1 acquisition included intravenous drug use (31%) and unprotected heterosexual (27%) and homosexual (24%) encounters. At the end of the follow-up period, CD4+ T-cell median was 557/μl and HIV-1 viral load median was 20 copies/ml. K103N was seen in 2 baseline tests. The most common acquired resistance mutations were M184V (70%), K103N (55%), and thymidine analogue mutations (TAM). There was 1 patient with integrase strand transfer inhibitor (INSTI) mutation. Virologic control among patients with acquired resistance was achieved with protease inhibitor (PI) based or PI-(INSTI)-combined regimens.

Conclusions:
M184V, K103N, and TAM were the most common resistance mutations. INSTI mutation was seen in only 1 patient. PI and PI-INSTI combinations achieved HIV-1 viral load suppression in patients with resistance mutations.