Indirect immunofluorescence test performance and questionnaire results from the Centers for Disease Control Model Performance Evaluation Program for human immunodeficiency virus type 1 testing

Results from laboratories performing indirect immunofluorescence (IIF) testing for human immunodeficiency virus type 1 antibody and participating in the Centers for Disease Control Model Performance Evaluation Program in 1988 are presented. Approximately 90% of all laboratories receiving specimen panels or questionnaires furnished results to the Centers for Disease Control. In September 1988, 111 reports were received from IIF laboratories from 34 states and nine countries; most of these laboratories did IIF testing in conjunction with other antibody tests. Hospital laboratories were the most common type of laboratory participating in the program. Laboratories that performed IIF employed fewer personnel and performed testing less frequently than did laboratories that performed enzyme immunoassays or Western blot (immunoblot) tests and were less likely to use a commercial test kit. Most of the laboratories that referred specimens for IIF testing sent them to the state laboratory. The analytic specificity for the Model Performance Evaluation Program specimens was 98.5% when indeterminate results on a negative specimen were considered correct (negative) and 89.6% when indeterminate results on a negative specimen were considered incorrect; analytic sensitivity was 94.8% when indeterminate results on a positive specimen were considered correct (positive) and 91.4% when indeterminate results on a positive specimen were considered incorrect. When indeterminate results were considered correct, all types of laboratories (blood bank, state, hospital, independent, and other) had analytic specificities over 96%, and all manufacturers had analytic specificities above 95%. All types of laboratories had analytic sensitivities over 92%, and analytic sensitivities were above 94% for all manufacturers and reagent sources except Cellular Products. Comparison of percentages of correct responses between IIF and Western blot assays on those samples for which there was good agreement on the target interpretation revealed no significant differences. Both individual donor and diluted materials were included in the evaluations; the diluted donor material presented the greatest testing difficulty. Within-survey reproducibility was about 93% overall and by specimen type. Between-survey reproducibility was about 81% for negative and indeterminate specimens and 88.5% for positive specimens, for an overall between-survey reproducibility of 84.3%. Differences in performance were noted when results were compared by type of laboratory and test manufacturer.