In 2017, Zimbabwe adopted a modified version of the World Health Organization 2016 recommendation on HIV birth testing by offering HIV testing at birth only to infants at “high risk” of HIV transmission (criteria based on timing of maternal diagnosis, viral load, and ART adherence). However, there is paucity of evidence on sensitivity, specificity and predictive value for this approach. This study focuses on assessing the sensitivity and specificity of birth testing “high risk” infants only compared to birth testing of all HIV-exposed infants.
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This was an analytic cross-sectional study. A five-question maternal risk screening tool based on the national guidelines definition of risk was administered to mothers of all HIV-exposed infants identified within 48 hours of birth at 10 study sites from November 2018 to July 2019. At these sites, a nucleic acid HIV test was performed on all HIV-exposed infants irrespective of risk status. Univariate and bivariate analysis were used to estimate the performance of the risk screening tool.
A total of 2,080 infants were enrolled. A nucleic acid test for HIV was successfully performed on 1,970 infants (95%) of whom 266 (13.5%) were classified as high risk infants. HIV prevalence for all infants tested was 1.5% (95% CI: 1%—2%) while prevalence among high risk infants and low risk infants was 6.8% (95%CI: 3.7%—9.8%) and 0.6% (95%CI: 0.3%—1%) respectively. There was a significant association between maternal HIV transmission risk status and HIV infection (p-value <0.001). Sensitivity and specificity of the maternal risk screening tool was at 62.1% (95%CI: 44.4%—79.7%) and 87.2% (95%CI: 85.7%—88.7%), respectively; positive and negative predictive values were 6.8% (95%CI: 3.7%—9.8%) and 99.4% (95%CI: 99.0%—99.7%) respectively Sensitivity and specificity in detecting HIV status varied for different individual screening questions. A ‘yes’ response to starting ART after 32 weeks’ gestation had the highest sensitivity in predicting HIV infection 58.6%, (95%CI: 40.7—76.5) and a ‘yes’ to non-adherence to ART had the lowest sensitivity 7.1% (95%CI: -2.4%—16.7%).
Although there was a significant association of maternal risk stratification with risk of infant infection and the negative predictive value of the risk screening tool was relatively high, the sensitivity was relatively low, and 38% of infants infected at birth would be missed if birth testing was based solely on a positive risk screen.