Evaluating the performance of the GeneXpert HIV-1 qualitative assay as a consecutive test for a new early infant diagnosis algorithm in South Africa.

BACKGROUND: The proportion of HIV-exposed infants and young children infected with HIV in South Africa (SA) has declined markedly over the past decade as a result of the country's comprehensive prevention of mother-to-child transmission programme. This decrease has in turn reduced the positive predictive value (PPV) of diagnostic assays, necessitating review of early infant diagnosis (EID) algorithms to ensure improved accuracy. OBJECTIVES: To evaluate the performance of the GeneXpert HIV-1 qualitative assay (Xpert EID) as a consecutive test for infants with an 'HIV-detected' polymerase chain reaction screening test at birth. METHODS: We retrospectively analysed a longitudinal cohort of HIV-exposed infants on whom birth testing was performed, using whole-blood ethylenediaminetetra-acetic acid samples, from four tertiary sites in Gauteng Province between June 2014 and December 2019. Birth samples from all infants with a Cobas AmpliPrep/Cobas TaqMan HIV-1 Qualitative Test v2.0 (CAP/CTM v2.0) HIV-detected screening test, a concurrent Xpert EID test and a subsequent confirmatory CAP/CTM v2.0 test on a separate specimen were included. Performance of the Xpert EID in predicting final HIV status was determined as proportions with 95% confidence intervals (CIs). A comparison of indeterminate CAP/CTM v2.0 results, as per National Health Laboratory Service resulting practice, with discordant CAP/CTM v2.0 v. Xpert EID results was performed. RESULTS: Of 150 infants who met the inclusion criteria, 6 (3.9%) had an Xpert EID result discordant with final HIV status: 5 (3.3%) were false negatives and 1 (0.7%) was false positive. As a consecutive test, the Xpert EID yielded a sensitivity of 96.5% (95% CI 92 - 98.9), specificity of 85.7% (95% CI 42.1 - 99.6), PPV of 99.3% (95% CI 95.7 - 99.9), negative predictive value of 54.5% (95% CI 32.5 - 74.9) and overall accuracy of 96.1% (95% CI 91.5 - 98.5). Using discordant CAP/CTM v2.0/Xpert EID results as criteria to verify indeterminate results instead of current practice would have reduced the number of indeterminate screening results by 42.1%, from 18 (12.6%) to 11 (7.2%), without increasing the false-positive rate. CONCLUSIONS: Addition of the Xpert EID as a consecutive test for specimens with an HIV-detected PCR screening result has the potential to improve the PPV and reduce the indeterminate rate, thereby reducing diagnostic challenges and time to final status, in SA's EID programme.

The next generation: Pregnancy in adolescents and women living with perinatally acquired HIV in South Africa.

BACKGROUND: An increasing number of girls living with perinatally acquired HIV (PHIV) are reaching adolescence and adulthood and becoming pregnant. Youth living with PHIV (YLPHIV) may have HIV-associated infections/complications, long-term exposure to antiretroviral treatment (ART), drug resistance and increased psychosocial challenges, which may adversely affect pregnancy outcomes. There is a lack of published studies on pregnancy in YLPHIV in sub-Saharan Africa. Objectives. To describe characteristics of pregnant South African (SA) YLPHIV and their pregnancy outcomes. METHODS: We retrospectively identified pregnancies in YLPHIV, who were diagnosed with HIV when they were <12 years old and before their first pregnancy (as a proxy for perinatal route of infection), from routinely collected data in Western Cape Province, SA (2007 - 2018). We combined these with pregnancies from a Johannesburg cohort of YLPHIV. Results. We identified 258 pregnancies among 232 females living with likely PHIV; 38.8% of pregnancies occurred in YLPHIV ≤16 years old, 39.1% at age 17 - 19 years and 22.1% at age ≥20 years. In recent years, a steady increase in the number of pregnancies in YLPHIV was noted; more than two-thirds occurred during 2016 - 2018. ART was commenced prior to pregnancy in 84.9% of YLPHIV, during pregnancy in 6.6% and was not commenced by pregnancy end date in 8.5%. Of the pregnancies in young women with documented outcomes (88.8%; n=229), 80.3% were live births, 14.4% terminations, 3.1% miscarriages and 2.2% stillbirths. Mother-to-child transmission of HIV occurred in 2.2% of infants, 75.3% were uninfected when last tested and 22.6% had unknown HIV status. Among YLPHIV with CD4 counts available within 12 months of pregnancy end date (n=202), 20.3% had a CD4 count <200 cells/µL, 43.1% CD4 count 200 - 499 cells/µL and 36.6% CD4 count ≥500 cells/µL. Among those with a viral load (VL) available within 12 months of pregnancy end date (n=219), 66.7% had a VL <400 copies/mL, 5.0% VL 400 - 999 copies/mL and 28.3% VL ≥1 000 copies/mL. Of 186 neonates, 20.4% were preterm deliveries (<37 weeks' gestation). Among neonates with known birthweight (n=176), the mean birthweight was 2 900 g (95% confidence interval (CI) 2 747 - 2 935 g) and 20.5% had a low birthweight (<2 500 g). One congenital malformation (musculoskeletal) and 2 neonatal deaths were recorded. CONCLUSIONS: In recent years, the number of pregnancies in YLPHIV has increased. A considerable proportion of pregnancies occurred in YLPHIV ≤16 years old. A high proportion of pregnancies was electively terminated. The prevalence of elevated VL and poor immunological status among pregnant YLPHIV is concerning.