Early Diagnosis of Human Immunodeficiency Virus Infection by p24 Antigen Detection

p24 antigen was estimated in human immunodeficiency virus (HIV) sero-negative individuals attending various sexually transmitted diseases (STD) clinics and also in sero-negative voluntary blood donors. A total of 300 STD cases and 500 voluntary blood donors, who also acted as controls, were included in this study. Antibody to HIV was detected by ELISA and was confirmed by western blot. In sero-negative individuals, p24 antigen detection was carried out by standard assay and immune-complex dissociation assay (ICD assay) using ELISA method and confirmation was done by neutralisation assay. In voluntary blood donors, 4 (0.8%) individuals were found to be HIV positive and no sero-negative individual was positive for p24 antigen. 41 out of 300 patients attending STD clinics were found to be positive for HIV and in 259 sero-negative patients, p24 antigen was detected in 6 (2.3%) cases by ICD assay whereas only 4 cases were detected by standard assay. By estimating p24 antigen an additional 2.3% HIV positive cases that were in window period were detected. Further, an ICD assay improves the detection of p24 positive individuals.