Antibody to hepatitis C (anti C 100-3) in French hemophiliacs.

486 patients followed in four French hemophilia centres were tested for antibody to hepatitis C virus C100-3 recombinant protein. On samples collected in 1989, the overall incidence of anti-C 100-3 positivity was 66%. None of the 27 patients only exposed to solvent-detergent treated factor VIII or IX concentrates had C 100-3 antibodies. There was no difference according to the type of hemophilia nor to its severity. Serological follow-up from 1985 to 1989 was carried out on 51 patients. Two third of the C-100 3 paradoxically seronegative patients in 1989 were in fact positive for these antibodies within the last 5 years. They have lost their HCV antibodies as seen with the presently available C 100-3 test. Actually, as the virus has been already present at least for the last 10 years, (on 51 samples collected in 1979, the incidence of C-100-3 positivity was 78%), all treated patients may well have been in contact with HCV.