Routine tests for HIV antigen [letter].

Testing serum for the p24 protein 1 of the antigens of HIV has proved helpful in the follow-up of individuals known to be HIV antibody positive. It has been reported that HIV antigenemia can sometimes be detected before antibody. What has not yet been established is whether systematic antigen testing is justified for early diagnosis or prevention. The authors have tested for HIV antigen 1000 samples sent for antibody testing and found 15 samples reactive in the antigen enzyme immunoassay test of which 7 could be neutralized and confirmed as antigen positive. It is concluded that testing for p24 antigen in a population of this type has little chance of detecting more infected individuals. In antibody negative subjects the search for antigen should perhaps be limited to special cases where a serological follow-up is done after an event carrying the risk of contamination. It is necessary to check the specificity of positive reactions by neutralization with antibody because of the high frequency of non-specific reactions in the enzume immunoassay test.