Early infant diagnosis (EID) of HIV immediately after birth allows for rapid initiation of treatment in HIV+ infants, limiting disease progression and restricting viral reservoir seeding. However, no standardized testing algorithm is currently recommended.
From April 2015-July 2018, the Early Infant Treatment Study (EIT) screened HIV-exposed infants in Botswana < 96 hours from delivery by Roche TaqMan qualitative DNA PCR. A negative DNA PCR test was defined as no HIV DNA amplification (target not detected) at initial dried blood spot screening; a positive as two concordant spots from same sample with target detected at any cycle threshold (Ct) value; and indeterminate as discordant spots (target detected/target not detected) from same sample. Repeat blood draw occurred for initial positive and indeterminate results. Quantitative HIV-1 RNA testing occurred for those presumptively enrolled in the study. We compared Ct values by the ultimate HIV status of the child (as confirmed by subsequent HIV-1 DNA, and when possible DNA/RNA, testing).
Of 10622 HIV-exposed infants screened, 10549 (99.3%) tested negative, 42 (0.4%) tested positive, and 31 (0.3%) tested indeterminate at the first HIV screening test. On repeat testing, 40 (95.2%) of the initial 42 positive infants remained positive and 2 (4.8%) tested negative. Of the 31 indeterminates, repeat testing confirmed 29 (93.5%) as negative and 2 (6.5%) as positive. Confirmatory testing of all positives and indeterminates re-classified 4 (5.5%) infants in total; 1 (1.4%) of the indeterminates required further HIV RNA testing to become reclassified as positive. Median DNA PCR Ct value at screening was 28.1 (IQR 19.8, 34.8) for all positive results and 35.5 (IQR 32.8, 41.4) for indeterminates (p<0.0001). Only 6 (8.2%) infants with final HIV+ status had Ct value > 33 at first screen, and only 2 (6.5%) with indeterminate result and Ct value < 33 at first screen had a final negative HIV status.
Using a standard cycle threshold of 33 and a confirmatory second blood draw for HIV DNA and RNA, our test algorithm appeared to eliminate the risk for false positive HIV results in the first week of life. Infants with Ct >33 should be re-tested with follow-up sampling, to minimize the risk for false positive testing.