HUMAN-IMMUNODEFICIENCY-VIRUS SPECIFIC IGA IN INFANTS BORN TO HUMAN-IMMUNODEFICIENCY-VIRUS SEROPOSITIVE WOMEN

Objective: To determine the sensitivity and specificity of human immun odeficiency virus (HIV)-specific IgA for vertically transmitted HIV in fection, particularly during the first month of life. Design/Setting/P atients: Prospective cohort study of 140 infants born to HIV-seroposit ive women in a large urban teaching hospital and of 248 older infants and children referred for diagnosis and treatment of HIV infection. Ma in Outcome Measures: The HIV-specific IgA immunoblot results were comp ared with the infection status of patients as determined by Centers fo r Disease Control and Prevention (Atlanta, Ga) criteria or by sequenti al early diagnostic assays for HIV. Sensitivity, specificity, and pred ictive values were calculated for each age range. Results: Among infan ts studied from birth, the rate of vertical transmission of HIV was 21 .6% (25/116). The sensitivity of HIV-specific IgA for the first month of life was 8.0% (2/25), and the specificity was 90.1% (82/91). Sensit ivity increased progressively during the first year of life, and the n egative predictive value was 94.6% by 6 to 8 months of age. The positi ve predictive value of this assay was 18.2% for neonates but was 96% t o 100% after the first month of life. Conclusions: False-positive test results for HIV-specific IgA occurred with diminishing frequency duri ng the first 4 weeks of life, and the frequency of detectable HIV-spec ific IgA was similar among the HIV-infected and uninfected groups at t his age. Beyond 1 month of age, detection of HIV-specific IgA is highl y specific and is a useful serum-based assay for early diagnosis of HI V infection. These results suggest that maternal-fetal transfusion is common and support the hypothesis that the majority of maternal-fetal transmission of HIV occurs around the time of parturition.