Use of laboratory tests and clinical symptoms for identification of primary HIV infection

Objective: To determine the sensitivity and specificity of symptoms, three HIV-1 RNA assays, a p24 antigen EIA and a third-generation enzyme immunoassay (EIA) antibody test for diagnosis of primary HIV infection (PHI). Design: Prospective cohort in a university research program. Participants: Of 258 eligible persons screened for PHI, 40 had primary/early infection (22 preseroconversion, 18 within 6 months of seroconversion) and 218 did not. Seven participants with preseroconversion HIV-1 from a second center were added for evaluating laboratory tests. Main outcome measure: PHI, defined as a negative or indeterminate antibody test with subsequent conversion. Symptom analysis also included persons with antibody conversion of less than 6 months' duration. Results: The symptoms most strongly associated with PHI in multivariate analysis were fever odds ratio (OR) 3.2; 95% confidence interval (0) 2.3-11.71 and rash (OR 4.8; 95% Cl 2.4-9.8). The sensitivity and specificity, respectively, for detecting preseroconversion HIV infection were: p24 antigen, 79% and 99%; third-generation EIA, 79% and 97%; HIV-1 RNA by branched chain DNA 100% and 95%; HIV-1 RNA by polymerase chain reaction 100% and 97%; HIV-1 RNA by transcription-mediated amplification testing, 100% and 98%. False-positive HIV-1 RNA tests were not reproducible and had values < 3000 copies/ml, while only one person with confirmed PHI was in this range. Conclusions: Rash and fever indicated the highest risk of PHI. HIV-1 RNA tests are very sensitive for PHI but false-positive results occur. False-positive results can be reduced through duplicate testing and considering tests < 5000 copies/ml as indeterminate results requiring additional testing. p24 antigen was more specific than HIV-1 RNA testing but less sensitive. (C) 2002 Lippincott Williams Wilkins.