Implementing an indeterminate range would support more accurate nucleic acid-based early infant diagnosis of HIV and likely reduce the number of infants put on lifelong treatment unnecessarily, according to data from a systemic review presented at the 10th IAS (International AIDS Society) Conference on HIV Science, held July 21-24, in Mexico City, Mexico,

Mother to child transmission of HIV has decreased significantly, which has caused a concern for false positives as a result of lowering positive predictive values. There is also limited guidance available for interpreting low levels of viremia in infants exposed to HIV. To help address this issue, researchers conducted a systemic review that identified 32 studies from 14 countries and included data from more than 1.3 million infants exposed to HIV. Meta-analyses of these studies calculated true positivity and false positivity across various proposed indeterminate thresholds.

The results showed that the optimal indeterminate range was the equivalent of a cycle threshold of 33 on the Roche COBAS TaqManHIV-1 Qualitative Test v2.0 assay. This represented the best trade-off between the percentage of infants with HIV who would be inaccurately identified as indeterminate and the percentage of uninfected infants who would start unnecessary treatment: approximately 8.43% and 6.66%, respectively. Implementing an indeterminate range was also shown to be cost-effective across most cycle threshold ranges.

In a survey of program managers (n=85), healthcare workers (n=146), and people living with HIV (n=587), more than 85% of respondents in each group believed that the use of an indeterminate range was acceptable in order to prevent infants being placed on unnecessary, lifelong treatment.

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According to investigators, most false positives would fall within the indeterminate range and receive further testing, rather than incorrectly being classified as HIV-positive. The investigators also noted that confirmatory testing, retention

during the exposure period, and end of exposure testing remain critical.

Reference

Vojnov L, Penazzato M, Sherman G, et al. Implementing an indeterminate range for more accurate early infant diagnosis: 2018 WHO recommendations. Presented at: 10th IAS Conference on HIV Science; July 21-24, 2019; Mexico City, MX. Abstract 2866.