WHO guidance recommends VL monitoring in pregnant women on ART to help identify high-risk infants for enhanced prophylaxis but there are few data evaluating this approach in routine care.
Data come from the screening procedures of a RCT of postpartum HIV care strategies at a large primary care clinic in Cape Town. In this setting VL monitoring takes place at the earlier of 12 weeks on ART, or 34 weeks’ gestation. In this context we identified consecutive HIV+ women initiating ART (TDF+FTC+EFV) who underwent VL testing during pregnancy, and for women with VL<400 copies/mL documented during pregnancy, repeated a VL within 4 weeks postpartum. All VL testing was done by the National Health Laboratory Services using the Abbott Realtime HIV-1 assay (Abbott Laboratories, Waltham, MA). We calculated sensitivity (SE), specificity (SP) and positive and negative likelihood ratios (LR+ and LR-) for antenatal VL<100 copies/ml in predicting peripartum VL<100 and <400 copies/mL, with sensitivity analyses examining subgroups of gestation at antenatal VL and prior ART exposure.
In 323 women (median age 28y, 40% with a history of previous ART), antenatal VL was taken at a median gestation of 33w (IQR 30-36), and at that time, 89.2% of women had a VL<100 copies/mL and 10.9% had a VL 100-400 copies/mL. Peripartum VL was taken at a median of 9 days (IQR 6-17) postpartum, at which point women were on ART for a median duration of 23w (IQR 18-28), and at that time 91.6%, 6.8% and 1.6% had VL<100, 100-400 and >400 copies/mL, respectively. The SE of antenatal VL<100 copies/mL in predicting peripartum VL<100 copies/mL was 0.95 (95% CI 0.92-0.97) and the corresponding SP was 0.74 (95% CI 0.54-0.89; LR+3.7, LR- 0.07). The ability of antenatal VL to predict peripartum VL was similar across strata of gestation at VL testing and history of ART use. Predictive performance was slightly weaker at thresholds of <400 copies/mL (LR+ 2.25, LR- 0.17).
These novel data suggest that antenatal VL<100 copies/mL is a useful predictor of peripartum viraemia and may be used to target enhanced PMTCT interventions in this setting. The high SE and low LR- suggest few women who are virologically suppressed during antenatal care subsequently become viraemic peripartum.