Reuse of ELISA Wells for HIV Antibody Testing

Abstract

ELISA testing for HIV antibody has been accepted as a standard method. For each test kit, it is commonly found that some reagents are left while all wells are used up. From March through July 1994, Chiangrai Regional Hospital which is located in one of the epicenters of the HI V/AIDS epidemic and uses the testing extensively conducted this study to determine feasibility of reuse of the wells which were exposed to HIV-negative sera. 288 wells were collected, rinsed with buffer solution, dried with tissue paper and refrigerated. The old wells were used for testing for anti-H I V antibody in comparison with the new ones (duplicate testing). Sera used in this study were randomly selected from the ones sent to the serology laboratory of the hospital. The prevalence of anti-HIV-positive was 15.2% with sensitivity, specificity, positive predictive value, and negative predictive value of 97.6%, 99.6%, 97.6% and 99.6% respectively. The reliability of the old wells as compared to the new ones as measured by kappa statistic was 97.3%. About two—thirds of the OD:cut-off ratios of the old wells were within 20% of those of the new ones. Although false positive and false negative rates were small, their clinical importance was immense. Therefore, reuse of ELISA wells should be limited only to estimation of HIV seroprevalence of high-risk groups where blood is tested in an unlinked and anonymous fashion and will not be used for transfusion, and to repeat testing of previously ELISA-tested HIV-positive sera.