HIV drug resistance interpreted by cumulative versus last genotypes in HIV-infected patients with multiple treatment failures.

Genotypic resistance test has been recommended to evaluate HIV drug resistance and guide the effective regimens of antiretroviral therapy (ART) in HIV-infected patients with treatment failure. In patients with multiple treatment failures, drug resistance-associated mutations may disappear due to the loss of selective drug pressure after switching regimens. A cohort study was conducted among HIV-infected patients who had ≥2 genotypic resistance tests during 2003-2011. HIV-1 pol nucleotide sequencing of reverse transcriptase and protease region was carried out using TRUGENE HIV-1 Genotypic Assay. Sequencing data was analyzed using Stanford rule-based interpretation algorithms. Of 54 patients with mean age of 30.1 years, 46.3% were males. HIV-1 subtype A/E was observed in 88.9% of patients. At the latest failure, 55.3% were receiving protease inhibitor-based regimens. Median CD4 and HIV RNA were 167 cells/mm(3) and 22,359 copies/mL. During a median duration of ART of 38.6 months, 72.2%, 22.2%, and 5.6% had 5, 3, and 2 genotype tests, respectively. When compared between using cumulative (CG) and last genotypes (LG), CG interpreted resistance to any drug 59.3% higher than LG did. For NRTI, NNRTI, and PI drug classes, CG interpreted as resistance 42.6%, 27.8%, and 7.4% higher than LG, respectively. The most common drugs that CG interpreted resistance with the higher rate than LG were lamivudine/emtricitabine, nevirapine, efavirenz, etravirine and abacavir. In conclusion, CG interprets HIV drug resistance at a higher rate than LG and may be more accurate to use for selecting the next effective regimen of ART among HIV-infected patients with multiple treatment failures.