Pilot study to estimate survivors to 1995 of 1983-1984 prevalent hepatitis C infections in Lothian patients who tested positive or negative for hepatitis B surface antigen in 1983-1984.

OBJECTIVE

To estimate Hepatitis C prevalence in 1983-1984, and survivorship to 1 January 1995, of patients who tested were for Hepatitis B surface antigen in 1983-1984; and to do so according to risk of blood-borne virus transmission, including injector status.

SETTING

Regional Virus Laboratory in Edinburgh.

SAMPLES

Sera from 1983-1984 which were originally received for hepatitis B surface antigen testing and were classified as being at high, medium, or low risk for blood-borne virus transmission.

RESULTS

Available 1983-1984 sera were tested from: (i) all 246 patients aged 15-55 years who were Hepatitis B surface antigen positive in 1983-1984; and (ii) a 10% systematic sample of 355 patients aged 15-55 years who had tested Hepatitis B surface antigen negative in 1983-1984. Patients' survival status at 1 January 1995 was established via the records of the Registrar General for Scotland. A Hepatitis C prevalent case cohort of 500 survivors to 1 January 1995- who were already infected with Hepatitis C in 1983-1984--could be established from group (i) and high or medium risk group (ii) patients with, as controls, 1460 individuals of similar age and risk group whose 1983-1984 sample was negative when tested retrospectively for Hepatitis C antibodies. Two hundred out of these 500 cases are not known to be injecting drug users, and the total would rise to 300 out of 600 if the case cohort were expanded to include low risk group (ii) surviving patients who were Hepatitis C antibody positive in 1983-1984. Between 82% (40/49) and 97% of injectors (57/59 if also HIV-infected) who were Hepatitis B surface antigen positive in 1983-1984 were already Hepatitis C antibody positive; and 72% (95% confidence interval (CI) 51%-93%) of injectors who were Hepatitis B surface antigen negative in 1983-1984 were nonetheless infected with Hepatitis C. Known drug user/contacts (excluding the major group of 59 identified HIV-infecteds) had Hepatitis C prevalence in 1983-1984 of 79% (53/67, with 95% CI 69%-89%), substantially higher than our prior assumption, which was 50%. Hepatitis C prevalence in 1983-1984 for patients who were not known to be injectors, were Hepatitis B surface antigen negative and were rated as moderate risk for blood-borne virus transmission was 13% (95% CI 4%-23%) and 8% (95% CI 3%-14%) even for low risk patients. Deaths by end December 1994 in 1983-1984 prevalent Hepatitis C infections were low: 2/35 (6%) for patients who were Hepatitis B surface antigen negative in 1983-1984 and 2/40 (5%) for Hepatitis B surface antigen positive injectors who were not HIV-infected. The latter rate with upper 95% confidence limit of 12% is modest when compared to the 10% mortality that would be expected of injectors over 11 years.

CONCLUSION

Retrospective Hepatitis C testing of 1700 stored sera from high or medium risk group (ii) patients who were not known to be injectors will identify an estimated 200 (11.7%) who were already Hepatitis C infected in 1983-1984 and still alive on 1 January 1995. Retrospective Hepatitis C testing of 1300 low risk samples is expected to yield 100 (7.6%) apparently non-injector patients who were already Hepatitis C infected in 1983-1984 and still alive on 1 January 1995.