Comparison of serologic assays and PCR for diagnosis of human herpesvirus 8 infection

A variety of assays for the diagnosis human herpesvirus 8 (HHV-8) infection have been reported. We compared several such assays with a panel of 88 spe cimens from human immunodeficiency virus (HIV)-infected patients with Kapos i's sarcoma (KS) (current-KS patients; n = 30), HIV-infected patients who l ater developed KS (later-KS patients; n = 13), HIV-infected patients withou t KS (no-KS patients; n = 25), and healthy blood donors (n = 20). PCR assay s were also performed with purified peripheral blood mononuclear cells (PBM Cs) to confirm positive serologic test results. The order of sensitivity of the serologic assays (most to Least) in detecting HHV-8 infection in curre nt-KS patients was the mouse monoclonal antibody-enhanced immunofluorescenc e assay (MIFA) for lytic antigen (97%), the orfK8.1 peptide enzyme immunoas say (EIA) (87%), the orf65 peptide EIA (87%), MIFA for latent antigen (83%) , the Advanced Biotechnologies, Inc, EIA (80%), and the orf65 immunoblot as say (80%). Combination of the results of the two peptide EIAs (combined pep tide EIAs) increased the sensitivity to 93%. For detection of infection in later-KS patients, the MIFA for lytic antigen (100%), the orfK8.1 peptide E IA (85%), and combined peptide EIAs (92%) were the most sensitive. Smaller percentages of no-KS patients were found to be positive (16 to 56%). Most p ositive specimens from the current-KS and later-KS groups were positive by multiple assays, while positive specimens from the no-KS group tended to be positive only by a single assay. PCR with PBMCs for portions of the HHV-8 orf65 rind gB genes were positive for less than half of current-KS and late r-KS patients and even fewer of the no-KS patients. The concordance between serologic assays was high. We propose screening by the combined peptide EI As. For specimens that test weakly positive, we recommend that MIFA for lyt ic antigen be done. A positive result with a titer of greater than or equal to 1:40 would be called HHV-8 positive. A negative or low titer would be c alled HHV-8 negative. If a population has a high percentage of persons who test positive by the combined peptide EIAs, then a MIFA could be performed with the negative specimens to determine if any positive specimens are bein g missed. Alternatively, if a population has a low percentage that test pos itive, then a MIFA could be performed with a subset of the negative specime ns for the same reason. As described above, only a titer of greater than or equal to 1:40) would be considered HHV-8 positive.