Evaluation of blood donors with equivocal hepatitis C serological results.

OBJECTIVE: To characterise blood donors with equivocal hepatitis C serological results and to develop an algorithm for their diagnosis and follow-up. DESIGN: Prospective case survey. SUBJECTS AND SETTING: 100 consecutive blood donors referred to the St Vincent's Hospital Liver Clinic, Victoria, with equivocal hepatitis C serological results (positive result for second generation Abbott Enzyme Immunoassay 2.0, but at least one negative result on supplemental testing by first generation Abbott neutralisation assay and Abbott Supplemental Assay for antibody to specific viral antigens). OUTCOME MEASURES: Percutaneous risk factors for hepatitis C exposure, peak serum alanine aminotransferase (ALT) levels, results of alternative immunoassay (Monolisa) and polymerase chain reaction (PCR) to detect hepatitis C viraemia. RESULTS: Thirty subjects had positive results for alternative immunoassay. A risk factor was identified for 32 subjects and was significantly associated (P < 0.01) with positive results for alternative immunoassay (23/32) and PCR (11/32), abnormal ALT levels (7/32), and strong reactivity on initial immunoassay (23/32). Presence of antibodies to both structural and non-structural antigens was also associated with risk factors and positive alternative immunoassay results. CONCLUSIONS: A definitive diagnosis was possible in 87% of subjects. A diagnosis of hepatitis C infection was based on positive alternative immunoassay results together with positive PCR results or presence of a risk factor. Hepatitis C was excluded for 60% of patients. The diagnosis for the remaining 13% remained indeterminate, indicating the need for a definitive diagnostic test for hepatitis C.