Promising antibody testing strategies for early infant HIV infection diagnosis in China.

Background: In China, 1.1% of people living with HIV were transmitted vertically, causing a heavy burden on families and society. Early infant diagnosis (EID) is critical for improving neonatal survival. The purpose of this study is to suggest improvement in antibody testing strategies with dried blood spots (DBSs) for EID in China through analysis of anti-HIV seroreversion of infants.

Methods: A total of 280 infants born to HIV infected mothers in four diverse provinces of China where multiple subtypes coexist were enrolled. The status of the infants' infection was determined by HIV antibody enzyme immunoassay and Western blot analysis at ≥ 18 months of age or by convincing clinical and epidemiologic data for deceased infants. A total of 1028 DBSs were collected during follow-up, which were tested to obtain anti-HIV signal to cut-off ratio (S/CO) data.

Results: For uninfected infants, anti-HIV S/CO decreased with age. Seropositivity percentage declined most rapidly at 6 months to 9 months of age and 98.7% children seroreverted by 12 months of age. For most infected infants, minimum S/CO values were obtained at ≤ 6 months of age. Antibody negative predictive value was 100% at ≥ 6 months of age. An S/CO increase ≥ 1.86 after three months follow-up can determine HIV infection. S/CO threshold of 3.17 can differentiate infected from uninfected infants for exposed kids at 9 months or older with sensitivity as 100% and specificity ≥ 94.2%.

Significance: Suggestions obtained through studying seroreversion data of Chinese HIV-exposed infants help improve antibody strategies for HIV EID in China. The infection can be determined as early as 3 months of age and excluded as early as 6 months of age.