Blood specimens were tested for CD4+ T-cell count and HIV RNA levels in laboratories participating in the AIDS Clinical Trials Quality Assurance Program. CD4+ count was categorized into three strata (i.e., >500, 200–500, and <200 CD4+ cells/mm3), and plasma HIV RNA level into four strata (i.e., <4000; 4000–20,000; 20,001–100,000; and >100,000 copies/mL); a total of 13 combined CD4+ / HIV RNA strata that were found to be relevant in prior studies(4,6), with HIV-negative women as the reference group.
