Diagnostic accuracy of fourth-generation ARCHITECT HIV Ag/Ab Combo assay and utility of signal-to-cutoff ratio to predict false-positive HIV tests in pregnancy

While the performance of the fourth-generation ARCHITECT HIV Ag/Ab Combo assay among pregnant women is comparable with that reported in nonpregnant populations, clinical implications of using a screening test with a positive predictive value of 83% in pregnancy are significant. When the qualitative RNA assay result is unavailable, absence of risk factors in combination with an ARCHITECT HIV Ag/Ab assay S/Co ratio <5 and nonreactive differentiation assay provide sufficient evidence to support deferral of unnecessary intrapartum interventions while awaiting qualitative RNA results.