Factors associated with the successful modification of antiretroviral therapy

Objectives: To assess the characteristics of medication regimen modification and the influence of a commercial genotypic resistance assay on the short-term (3–12 weeks) viral load response (≥ 0.5 log reduction) in HIV-1-infected patients extensively treated with antiretroviral therapy (ART). Methods: A nested cohort study was performed in two clinics from the HIV Outpatient Study of 96 persons with a HIV-1 viral load of 104 log copies/ml or greater taking at least two antiretroviral medications. Results: Successful modification was associated with adding at least two new medications [relative risk (RR), 1.5; 95% confidence interval (CI), 1.1–2.2], adding a drug from a previously unused class of agents (RR, 2.0; CI, 1.4–2.9), the initiation of a non-nucleoside reverse transcriptase inhibitor (NNRTI) (RR, 1.7; CI, 1.2–2.4), but not substituting a protease inhibitor or the use of a commercial genotypic resistance assay. Conclusion: Incorporating a drug from a previously unused class or changing at least two new medications, but, within the confines of this study, not using a commercial genotypic resistance assay, was associated with the successful modification of ART as measured by a reduction in viral load.