Reducing the cost of HIV antibody testing.

ABSTRACT

PIP: The cost-saving strategies of HIV antibody testing are assessed. The enzyme-linked immunosorbent assay (ELISA) is deemed the most efficient and reliable test for processing 100 samples/day in a large blood bank. Up to 82% can be saved if the western blot is replaced by a suitable ELISA or rapid or simple test. WHO has recommended testing for HIV antibody that uses ELISA with or without rapid and simple assays in place of the ELISA plus western blot strategy. The testing strategies recommended are as follows: 1) All serum is tested with one ELISA or a rapid or simple assay. Reactive samples are taken to be positive for HIV antibody and non-reactive samples to be HIV-antibody negative; 2) All serum is first tested as in strategy 1, and any sample reactive in the first assay is retested with a second ELISA or rapid/simple assay based on a different antigen preparation, a different test principle (indirect vs. competitive), or both; 3) All serum is first tested as in strategy 1, and any reactive samples are retested with a different assay. Strategy 3 requires a third test if the serum is reactive in the first and second assays. Screening for HIV antibody in pooled serum from up to 5 individuals can also reduce the cost. Pooling methods assessed in blood banking systems in Zaire, Zimbabwe, Ecuador, the Philippines, and the Caribbean proved to be as sensitive and specific as individual sample testing. The use of strategy 1 to test only pooled serum saves about 75%, and testing of pooled serum with subsequent identification of affected seropositive individuals saves about 55%. WHO recommends a maximum pool of 5 samples for areas with seroprevalence of 2%. The simple particle agglutination method on the pooled serum can also save costs. Test kits cost from $1.20 per test for ELISA to more than $30 for western blot. In 1990, the Global Program on AIDS bought HIV diagnostic test kits; a saving to countries of about 44% will be achieved through the bulk purchase of tests from kit manufactures.