Early infant diagnosis HIV-1 PCR cycle-threshold predicts infant viral load at birth

Indeterminate HIV PCR results within South Africa's early infant diagnosis programme, 2010-2019

OBJECTIVES

We describe the extent of, and variables associated with, indeterminate HIV-PCR results and final HIV status within South Africa's early infant diagnosis (EID) programme between 2010 and 2019.

METHODS

Retrospective analysis of routine paediatric HIV-PCR laboratory data from South Africa's National Health Laboratory Service Data Warehouse between 2010 and 2019. Final HIV status was determined by linking patient results (including HIV-PCR, HIV viral load, HIV serology and CD4 counts) using a probabilistic matching algorithm. Multivariate logistic regression was performed to determine variables associated with final HIV status among patients with an indeterminate HIV-PCR result.

RESULTS

Among 4 429 742 specimens registered for HIV-PCR testing from 3 816 166 patients, 113 209 (2.97%) tested positive and 22 899 (0.6%) tested indeterminate. As a proportion of HIV-detected results, 15.7% (23 896/151 832) of total and 31.5% (4900/15 566), 18.8% (11 400/60 794) and 10.1% (7596/75 472) among patients aged <7 days, 7 days-3 months and ≥3 months, respectively, were reported as indeterminate. Overall, 39.7% of patients with an indeterminate result had a linked HIV test to determine HIV status, of which 53.6% were positive with a median time to repeat testing of 30 days (interquartile range 15-69). Among patients who tested indeterminate, variables associated with a significantly higher odds of having a positive HIV status included testing indeterminate at birth (adjusted odds ratio (AOR) 0.63 (0.48-0.83) and 0.52 (0.39-0.69) for testing indeterminate at 7 days-3 months and ≥3 months respectively compared with birth), within a hospital (AOR 2.45 (1.99-3.03)), and in districts with an intra-uterine transmission rate ≥1.1% (AOR 3.14 (1.84-5.35)) (p < 0.001).

DISCUSSION

Indeterminate HIV-PCR results represent a considerable burden of missed diagnostic opportunities, diagnostic dilemmas and delays in making a definite diagnosis among HIV-infected infants within South Africa's EID programme. Alternative EID verification practices are urgently needed.

Evolving complexities of infant HIV diagnosis within Prevention of Mother-to-Child Transmission programs

Early diagnosis of HIV infection among infants and children is critical as prompt initiation of antiretroviral therapy prevents morbidity and death. Yet despite advances in the accuracy and availability of infant HIV diagnostic testing, there are increasing challenges with making an early definitive diagnosis. These challenges relate primarily to advances in prevention of mother-to-child transmission (PMTCT) of HIV. Although PMTCT programs have proven to be highly effective in reducing infant HIV infection, infants who are HIV-infected may achieve virological suppression and loss of detectability of HIV nucleic acid prior to diagnosis because of antiretroviral drug exposure. Hence, false-negative and indeterminate HIV polymerase chain reaction (PCR) results can occur, especially among high-risk infants given multi-drug prophylactic regimens. However, the infant HIV diagnostic landscape is also complicated by the inevitable decline in the positive predictive value of early infant diagnosis (EID) assays. As PMTCT programs successfully reduce the mother-to-child transmission rate, the proportion of false-positive EID results will increase. Consequently, false-negative and false-positive HIV PCR results are increasingly likely despite highly accurate diagnostic assays. The problem is compounded by the seemingly intractable prevalence of maternal HIV within some settings, resulting in a considerable absolute burden of HIV-infected infants despite a low mother-to-child transmission rate.