Virologic parameters as surrogate markers for clinical outcome in HIV-1 disease: verification, variation, and validation.

The criteria used to evaluate which virologic measurements are used to monitor HIV-1 infection should include an assessment of verification, variation, and validation. Rationale for use should first be based on understanding the role of the measurement in the pathogenesis of the disease. Subsequently, the prevalence of the measurement, an understanding of its intrinsic variation, and ease of use will determine the utility of the measure. The usefulness of the measurement will depend on its validation in relation to disease prognosis, antiviral activity, and antiviral efficacy.