To determine the duration and specificity of antibodies to hepatitis C virus in hepatitis B surface antigen-negative chronic active hepatitis, sera from 19 patients seropositive by enzyme immunoassay were assessed by recombinant immunoblot assay Only 12 of the 19 patients were reactive by immunoblot assay (63%). Patients nonreactive by immunoblot assay had lower signal-cutoff ratios by enzyme immunoassay (1.3 ± 0.2 vs. 6.5 ± 0.1; P < 0.05), higher serum immunoglobulin G levels (4082 ± 301 vs. 1760 ± 143 mg/dL; P < 0.05), and higher serum gamma globulin levels (3.3 ± 0.5 vs. 2.04 ± 0.1 g/dL; P < 0.05) than reactive patients. Twelve of 14 patients with serial studies remained seropositive after 39 ± 11 months of follow-up (range, 7-113 months). Only patients nonreactive by immunoblot assay became seronegative by enzyme immunoassay during corticosteroid therapy (2/3 vs. 0/6 patients). It is concluded that seropositivity by enzyme immunoassay may not be documented by immunoblot assay. Patients nonreactive by immunoblot assay have lower signal-cutoff ratios and higher gamma globulin levels than reactive patients, and their seropositivity may be nonspecific. Patients nonreactive by immunoblot assay may lose seropositivity by enzyme immunoassay during corticosteroid therapy.
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