Advantages of an alternative strategy based on consecutive HIV serological tests for detection of HIV antibodies in Central African Republic.

Voluntary testing and counselling are accepted widely for the prevention of human immunodeficiency virus (HIV) infection. Therefore, simple, accurate and affordable tests are required. The diagnosis strategy used in developed countries, based on an immunoblot confirmatory test, cannot be used on a large scale in developing countries because of its cost. Therefore, alternative strategies must be developed. In this study, we tested according UNAIDS and World Health Organisation recommendations for HIV testing strategies, a strategy based on two consecutive tests, using the mixed automatic enzyme immunoassays test Vidas HIV DUO as a screening test and Determine Abbott rapid immunochromatographic test as a confirmatory test. In first step, reference serum samples (113 HIV-positive and 167 HIV-negative) were used to evaluate the performance of both tests. In a second step, 876 serum samples from patients were used to compare the 'simultaneous' testing strategy currently used in Central African Republic (CAR) to the 'consecutive' testing strategy. The sensitivity and negative predictive value of both tests were 100%. The specificity and positive predictive value of Determine Abbott (>99%) were higher than those of Vidas HIV DUO (90.4 and 87.6%, respectively). In all cases in which the two tests gave discrepant results, the patient was considered HIV-negative after a second test carried out 2-4 weeks later since the optical density value of the Vidas HIV DUO of the second sample was not higher than that of the first sample. This new consecutive testing strategy appears to be reliable, simple and rapid, allowing counselling and results to be given on the same day, which we believe is important for improving post-test counselling. Furthermore, the consecutive testing strategy reduces the cost of testing, which is very important in developing countries.