A second generation ELISA for combined detection of antibodies to three hepatitis C virus (HCV) recombinant proteins, i.e. C100, C33c and core, was compared with a first generation anti-HCV ELISA in which only antibodies to C100 are detected. The results of the ELISAs were evaluated in 225 haemophilia patients (panel A) and 44 patients with non-A, non-B (NANB) hepatitis (panel B). HCV infection was established by cDNA-polymerase chain reaction (PCR) (in panel B only) and by studying the anti-HCV reaction patterns in 4 separate ELISAs for detection of antibodies to the recombinant proteins C100, C33c, core and a combination of two synthetic peptides sp67/65 derived from the C100 region. The sensitivity for the detection of HCV infection had increased from 0.92 [95% confidence interval (Cl) : 0.87-0.95] to 1.00 (95% Cl: 0.98-1.00) in haemophiliacs and from 0.84 (95% Cl: 0.66-0.95) to 1.00 (95% Cl: 0.89-1.00) in NANB hepatitis patients when the second generation ELISA was used instead of the first generation ELISA. Concurrently the chance of a false negative result was reduced in panel A and B from 0.37 to 0 and from 0.28 to 0, respectively. Analysis of anti-HCV reaction patterns revealed that 172 of 206 (83.5%) anti-HCV ELISA-reactive haemophilia patients had antibodies to all 4 antigens tested. In the NANB hepatitis patients 18 of 31 (58.1%) anti-HCV ELISA-reactive subjects reacted with 4 antigens. In the PCR tested panel of NANB hepatitis patients 2 subjects who showed antibody reactivity to only one antigen and 5 patients with reactivity to 2 antigens were PCR-positive. On the other hand, 1 NANB hepatitis patient showed antibody reactivities to all 4 antigens tested, but was PCR-negative. Antibodies to core were the most prevalent in the two populations studied. We conclude that the introduction of the second generation anti-HCV ELISA will significantly reduce the likelihood of unrecognized HCV infection.

Three commercially available 3rd-generation anti-HCV ELISAs (Abbott, Murex and Ortho) were evaluated in various serum panels: (A) blood donor samples (n = 403) with 1st- or 2nd-generation anti-HCV ELISA (various manufacturers) positive test results; (B) non-A, non-B hepatitis patients (n = 212); (C) multi- transfused patients (n = 253); (D) serial dilutions of HCV confirmed (RIBA and PCR) positive blood donors (n = 24), and (E) first-time blood donors (n = 1,055). All samples of panels A, B and C were tested in PCR and RIBA-2. In panels A, B and C, 398 samples were HCV PCR positive: all were detected by Abbott and Ortho, and 397 (99.7%) by Murex. The sample missed by the Murex ELISA showed an isolated anti-C33c reactivity in RIBA-2. In panels A-C, 442 samples were RIBA-2 positive and all were detected by the 3 tests. With Probit analysis on results of panel D, no significant difference in sensitivity was observed between the 3 evaluated ELISAs. Specificities of Abbott, Murex and Ortho in 1,055 blood donors were 99.7, 99.3 and 99.9%, respectively (NS, χ2). We conclude that the sensitivity and specificity of the 3 ELISAs are comparable although the C33c antigen in the Murex VK47 test should be improved.

Recently, an assay for detection of provirai HIV-1 DNA in leukocytes became commercially available. This assay (Amplicor HIV-1 test, Roche Diagnostic Systems) multiplies HIV-1 DNA up to a detectable level, using the polymerase chain reaction. We studied performance of this assay on 74 samples from HIV-1-infected patients and on 41 samples from healthy blood donors. Twice a negative control sample appeared to be erroneously reactive. However, sensitivity and specificity on the patient and donor samples both were 100%. To avoid false-positive results, we advise to repeat initially reactive samples if no other data confirm HIV-infection.

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