Early adoption of HIV-1 resistance testing in the San Diego County Ryan White CARE Act Program: predictors and...

This research identifies predictors and outcomes of early use of human immunodeficiency virus type 1 (HIV-1) resistance testing in the San Diego County Ryan White CARE Act program. Between January and November 2000, 98 patients receiving care in 7 clinics participated in the resistance testing program. Provider characteristics predictive of participation included number of patients and percent of practice devoted to HIV care and number of HIV-related continuing medical education hours over the preceding 12 months. Providers rarely requested expert panel review of test results, and expert review was not predictive of better viral load responses. Regimens specified before knowledge of resistance results had more active drugs than those prescribed after knowledge of test results. Phenotypic susceptibility was predictive of virologic response, as was degree of prior nucleoside analogue exposure. There was little relationship between phenotypic susceptibility and a clinician's decision to prescribe a drug. Early adopters of this technology were more experienced HIV providers than their colleagues and utilized susceptibility information using reasoning processes in which resistance was a contributory but not necessarily dominating factor.