Genotype and phenotype at baseline and at failure in human immunodeficiency virus-infected antiretroviral-naive patients in a randomized trial comparing zidovudine and lamivudine plus nelfinavir or nevirapine.

For the 127 Spanish patients enrolled in the Combine Study, a resistance substudy was performed with 100 (79%) plasma samples obtained at baseline and with 18 samples obtained from 19 patients at the time they experienced treatment failure. At baseline, primary mutations to nonnucleoside reverse-transcriptase inhibitors and protease inhibitors were not detected, whereas mutations to nucleoside reverse-transcriptase inhibitors were observed in 10% of patients. At failure, mutations were detected in 7 of 16 patients. An agreement in the results of virtual and real phenotypes was observed in the 93 samples in which both tests were performed.