Low and stable HIV seroprevalence in pregnant women in Shaba province, Zaire

Sentinel serosurveillance for HIV infection has been carried out in Shaba province, Zaire, among consecutive pregnant women attending antenatal clinics from 1989 to 1991. There were four surveillance sites (three urban and one semiurban), at which a total of 13 surveillance studies were made of 4,205 women. Overall, 3.1% were HIV seropositive. There were no significant differences in HIV seroprevalence between surveillance sites, and HIV seroprevalence did not increase at any of the surveillance sites during the 2-year period of study. Since changes in the population studied did not occur between surveillance studies, it is believed that the observed stable trend reflects stable HIV seroprevalence rates in the general adult population of the surveillance sites. Collateral HIV seroprevalence data were available from 8,725 blood donors at 20 sites (six urban, 14 rural) in the province, who had an overall HIV seroprevalence of 4.6%. The higher HIV seroprevalence rate among blood donors was probably due to selection bias, since HIV seroprevalence rates in two blood banks, which relied nearly exclusively on replacement donors, were 2.7 and 2.8%, our best estimate for HIV seroprevalence in the three cities where blood banks exist and where no surveillance studies were carried out. The stable and relatively low HIV seroprevalence rates in Shaba province are in sharp contrast with the rapidly increasing and much higher rates in neighboring Zambia and other East African cities. Reasons for this discrepancy are unclear, and their eludication may yield critical information for HIV prevention programs.

Prevention of blood-borne HIV transmission using a decentralized approach in Shaba, Zaire

OBJECTIVE

To prevent blood transfusion-acquired HIV infection with a decentralized approach to HIV screening of blood donors, using an instrument-free rapid test.

SETTING

Shaba province, Zaire (496,877 km2).

METHODS

The programme consisted of training health-care workers, distribution of a rapid HIV-antibody test (DuPont's HIVCHEK) for screening of all blood donations, and quality control of testing by a regional reference centre.

RESULTS

Over a 2-year period, 11,940 rapid tests were distributed to 37 hospitals, covering 75% of all hospital beds outside the copper mine's health system in Shaba. Eighty-five per cent of the tests were used to screen blood donors (5.4% positive test rate) and 13% to test patients (39.7% positive test rate). At least 265 cases of HIV-positive blood donation were prevented, at an estimated cost of 137-279 ECU per case. Only 26% of initially positive specimens reached the central laboratory for supplemental testing, and sterile transfusion equipment and blood-grouping reagents were frequently unavailable. The lack of transport and communications and a deteriorating health system were major constraints.

CONCLUSIONS

District hospitals in Africa are often long distances from major cities, difficult to reach for most of the year, and perform a small number of transfusions. In this context a classical centralized regional blood bank may not be a feasible option to ensure safe blood transfusions. However, safe blood transfusion can be achieved with a decentralized approach using a rapid test, provided that minimum standards of health-care services are available.

A simplified and less expensive strategy for confirming anti HIV-1 screening results in a diagnostic laboratory in Lubumbashi, Zaire

The conventional algorithm for HIV testing based on the confirmation of all positive anti-HIV screening reactions by Western blot (WB) is too expensive for developing countries. We investigated the validity of confirming positive screening assay reactions by a second screening test, limiting the use of the supplemental assay to the discrepant test results (algorithm 3), or screening all sera with 2 different assays and retesting all discrepant results by a supplemental assay (algorithm 4) on a panel of 519 sera in a regional reference laboratory in Lubumbashi, Zaire. Combining the Vironostika anti-HTLV-III ELISA with HIV Chek 1 + 2 or Clonatec Rapid HIV 1/2 Ab on all samples and retesting the discrepant results in WB or a line immunoassay (INNO-LIA) (algorithm 4), yielded a sensitivity of 100% and specificities of 98.4% and 99.0% respectively, at costs of 7.3 US $ and 9.3 US $ per test, respectively, for a 40% prevalence of HIV antibody positive samples. The conventional algorithm scored a sensitivity of 97.1% and a specificity of 100% for 11.3 US $ per test. The testing strategy of combining HIV Chek 1 + 2 and Clonatec Rapid HIV 1/2 Ab, an interesting option for small isolated centra, had a 96.6% sensitivity, but yielded only a slightly better specificity of 99.0%, as compared to 97.8% for HIV Chek alone. The price of combining the two simple assays using algorithm 3 was 6.8 US $ per test, using algorithm 4 was 10.6 US $. HIV testing strategies based on ELISA and a simple HIV test are a valuable alternative for reference laboratories faced with a high prevalence of HIV positive samples.