Recognition of infants at high risk for vertical HIV transmission at delivery in rural Western Cape Province, South Africa.

Background: Despite South Africa’s substantial reduction in vertical HIV transmission (VHT), national paediatric HIV elimination is not yet attained. National and Western Cape Province (WC) HIV guidelines recommend enhanced postnatal prophylaxis for infants at high risk for VHT, identified in the WC 2015/2016 guidelines by any single high-risk criterion (maternal antiretroviral therapy (ART) <12 weeks, absent/ unsuppressed maternal HIV viral load (HIV-VL) <12 weeks before/including delivery, spontaneous preterm labour, prolonged rupture of membranes, chorioamnionitis). Accuracy of high-risk infant identification is unknown.

Objectives: Primarily, to determine the proportion of infants at high risk for VHT, the accuracy of labour-ward risk classification, the criteria determining high-risk statuses and the criteria missed among unrecognised high-risk infants; secondarily, to determine maternal factors associated with high-risk infants.

Methods: Infants born to women living with HIV at a rural regional hospital (May 2016 - April 2017) were retrospectively evaluated using data from the labour ward VHT register, standardised maternity case records, National Health Laboratory Service database and WC Provincial Health Data Centre. The study-derived risk status for each infant was determined using documented presence/absence of risk criteria and compared with labour ward assigned risk to determine accuracy. Proportions of high-risk and unrecognised high-risk infants with each high-risk criterion were determined. Maternal characteristics associated with having a high-risk infant were evaluated using multivariable logistic regression.

Results: For liveborn infants, labour ward assigned risk classifications were 40% (n=75/188) high risk, 50% (n=94/188) low risk and 10% (n=19/188) unclassified. Study-derived risk was high risk for 69% (n=129/188) and low risk for 31% (n=59/188), yielding a high-risk classification sensitivity of 51% (95% confidence interval (CI) 42 - 60) and specificity of 69% (95% CI 56 - 80). Absent/unsuppressed HIVVL <12 weeks before delivery accounted for 83% (n=119/143) of study-derived high-risk exposures and 81% (n=60/74) of missed high-risk exposures. Fewer mothers of high-risk infants had >4 antenatal visits (38% v. 81%, p<0.01) and first antenatal visit <20 weeks’ gestation (57% v. 77%, p=0.01). Only the number of antenatal visits remained associated with having a high-risk infant after adjusting for gestation at first visit and timing of HIV diagnosis and ART initiation: each additional antenatal visit conferred a 39% (95% CI 25 - 50) reduction in the odds of having a high-risk infant.

Conclusion: Labour ward risk classification failed to recognise half of high-risk infants. Infant high-risk status as well as non-detection thereof were driven by suboptimal maternal HIV-VL monitoring. Reinforcing visit frequency later in pregnancy may improve antenatal HIV-VL monitoring, and point-of-care HIV-VL monitoring at delivery could improve recognition of virally unsuppressed mothers and their high-risk infants.