Analysis of undetectable HIV RNA using survival analysis: results must be interpreted carefully.

This methodological note exemplifies the drawbacks of conventional survival analysis for studying the determinants of the evolution of HIV RNA after the initiation of a HAART regimen in observational cohort studies. The potential for loss of information might yield differential misclassification biases and therefore unreliable results. Longitudinal models are better suited to analyze the repeated measures of a continuous outcome such as HIV RNA.