Phenotypic Drug Susceptibility Testing Predicts Long-Term Virologic Suppression Better than Treatment History in Patients with Human Immunodeficiency Virus Infection

ceptibility were evaluated. In multivariate analyses, phenotypic susceptibility was an independent predictor of time to treatment failure (adjusted hazards ratio [HR], 0.70; 95% confidence interval [CI], 0.55‐0.90; and adjusted HR, 0.76; 95% CI, 0.61‐0.95, with reduced drug susceptibility cutoffs defined as 4.0-fold and 2.5-fold higher than reference virus IC50 values, respectively). Previous protease inhibitor experience was also a significant independent predictor. Notably, drug susceptibility predicted on the basis of treatment history alone was not predictive of time to treatment failure. In this cohort, phenotypic testing results enhanced the ability to predict sustained long-term suppression of virus load.