Centrifugation improves the detection of HIV-1 p24 antigen in plasma from children born to mothers infected with HIV-1

Detection of HIV proteins and/or nucleic acids is necessary for the diagnosis of perinatal HIV infection. Despite its low sensitivity, detection of p24 antigen in plasma is a simple and economic method for the diagnosis of HIV in exposed children. The aim of this study was to improve the sensitivity of detection of p24 using centrifugation of plasma.Forty-seven selected stored samples from 37 children (23 infected, 14 uninfected, median age of 137 days) were examined. Plasma samples (volume 0.3–1.5 ml) were defrosted, centrifuged at 23,500 × g at 4 °C for 60 min and determination of p24 was carried out in the resuspended pellet (0.12 ml).In 32 plasma samples from infected children, p24 was found originally in 6 (18.7%) and resulted positive in 24 (75%) pellets. When only one sample per child was considered, sensitivity was significantly higher in pellets, 3/23 uncentrifuged plasma samples and 15/23 pellets (McNemar Test, p < 0.001). Specificity was 100%. The absorbance/cut-off ratio was always higher in the pellets from positive children (p = 0.028). Plasma samples with volumes of 1 ml or more achieved a higher sensitivity (91.7% vs. 36.4%, p = 0.009).Centrifugation of plasma samples prior to determination of p24 in pediatric patients resulted in a significant increase in sensitivity.