An algorithm to optimize viral load testing in HIV-positive patients with suspected first-line antiretroviral therapy failure in Cambodia

J Acquir Immune Defic Syndr. 2009 Sep 1;52(1):40-8. doi: 10.1097/QAI.0b013e3181af6705.


Objective: To develop an algorithm for optimal use of viral load testing in patients with suspected first-line antiretroviral treatment (ART) failure.

Methods: Data from a cohort of patients on first-line ART in Cambodia were analyzed in a cross-sectional way to detect markers for treatment failure. Markers with an adjusted likelihood ratio <0.67 or >1.5 were retained to calculate a predictor score. The accuracy of a 2-step algorithm based on this score followed by targeted viral load testing was compared with World Health Organization criteria for suspected treatment failure.

Results: One thousand eight hundred three viral load measurements of 764 patients were available for analysis. Prior ART exposure, CD4 count below baseline, 25% and 50% drop from peak CD4 count, hemoglobin drop of > or =1 g/dL, CD4 count <100 cells per microliter after 12 months of treatment, new onset of papular pruritic eruption, and visual analog scale <95% were included in the predictor score. A score >or=2 had the best combination of sensitivity and specificity and required confirmatory viral load testing for only 9% of patients. World Health Organization criteria had a similar sensitivity but a lower specificity and required viral load testing for 24.9% of patients.

Conclusion: An algorithm combining a predictor score with targeted viral load testing in patients with an intermediate probability of failure optimizes the use of scarce resources.

Publication types

  • Evaluation Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Algorithms
  • Antiretroviral Therapy, Highly Active
  • Cross-Sectional Studies
  • Drug Resistance, Viral / drug effects
  • Female
  • HIV Infections / drug therapy*
  • HIV Infections / virology*
  • HIV-1 / isolation & purification*
  • Humans
  • Male
  • Middle Aged
  • Sensitivity and Specificity
  • Treatment Failure
  • Viral Load / methods*
  • Young Adult