HIV diagnostic algorithm requires confirmatory testing for initial indeterminate or positive screens in the first week of life

Abstract

Background: Risk for nondiagnostic and false-positive HIV testing has not been quantified for neonates.

Methods: From April 2015 to July 2018, we screened HIV-exposed infants in Botswana less than 96 h from birth by qualitative DNA PCR. Repeat blood draws for DNA and RNA PCR testing occurred for initial positive and indeterminate results to establish final diagnosis. We compared screening DNA PCR cycle threshold values with final HIV status of the child.

Results: Of 10 622 HIV-exposed infants, 10 549 (99.3%) had no HIV DNA detected (negative), 42 (0.4%) had HIV DNA detected (positive), and 31 (0.3%) tested indeterminate at first HIV screen. Repeat testing identified 2 (5.0%) of 40 positive screens (2 declined additional testing) as false positives and confirmed 2 (6.5%) of 31 indeterminate screens as infected. Median cycle threshold value at screening was 28.1 (IQR 19.8--34.8) for children with final positive status, and 35.5 (IQR 32.8--41.4) for indeterminates who were ultimately negative. Six (15%) of 40 infants with final positive status had cycle threshold value greater than 33 at first screen, whereas 3 (9.7%) of 31 indeterminates with final negative status had cycle threshold value 33 or less at first screen. This threshold resulted in a negative predictive value of 82% and a positive predictive value of 92% for a single screen.

Conclusion: Although a DNA PCR cycle threshold value of 33 was predictive of the final HIV status in newborns, overlap occurred for true positives, false positives, and initial indeterminates. Testing additional samples should be standard practice for positive and indeterminate HIV DNA PCR tests in the first week of life.

Conflict of interest statement

Competing interest: The authors declare that they have no competing interests.

Figures

Figure 1:

Early Infant Trial Screening Flowchart

Figure 2:

Comparison of Ct values for all infants who initially screened indeterminate or positive, showing initial and repeat HIV PCR testing and grouped by final HIV status Note: Initial screening consisted of dried blood spot HIV DNA PCR testing on a single spot (Spot 1), and negative results (N=10,549) were not tested further (data not shown). For all initial Spot 1 tests with any HIV DNA target detection at any cycle threshold, a second spot (Spot 2) was performed. Follow-up testing was performed on a second blood sample for all initially positive or indeterminate tests, with 1 or 2 spots tested (Spot 3 and Spot 4). * Testing occurred if initial results from spot 1 & 2 were discordant or differed from that from spot 3. TND – Target not detected