COLLABORATIVE STUDY FOR THE EVALUATION OF ENZYME-LINKED IMMUNOSORBENTASSAYS USED TO MEASURE HUMAN-ANTIBODIES TO BORDETELLA-PERTUSSIS ANTIGENS

Acellular pertussis vaccines are being evaluated in multiple clinical studies, and human immunogenicity data will likely be pivotal in the a ppraisal of vaccine responses between populations and the responses to different vaccine combinations. Antibody response to pertussis antige ns is also used in the diagnosis of pertussis. An international study was designed to assess the comparability of data generated in differen t laboratories by enzyme-linked immunosorbent assays (ELISAs). Thirty- three participating laboratories were asked to quantitate specific ant ibody to pertussis toxin (PT), filamentous hemagglutinin (FHA), pertac tin (PRN), or fimbrial proteins (FIM) in 21 samples. Samples were to b e assayed in triplicate in five independent assays by each ELISA routi nely performed in the laboratory to assess intra-assay, interassay, an d population variability. The mean sample values were used to compare quantitative results among the laboratories. Thirteen of the 32 labora tories which submitted evaluable data for an assay to measure antibodi es to PT, 12 of 30 laboratories with assays for FHA, 10 of 17 laborato ries with assays for PRN, and 6 of 13 laboratories with assays for FIM maintained a coefficient of variation below 20% for 75% of the sample s tested. Assays that measure antibodies to FIM appear to be less prec ise than the other assays. Precision varied among laboratories that us ed similar methods. The relative values of intra- and interassay varia bilities were not consistent for a given assay within a laboratory, in dicating that the sources of these variability components may be unrel ated. Precision and agreement appeared less reliable for samples with low antibody levels. Ranking and regression analyses suggest that some laboratories generated comparable quantitative results, although dire ct comparison or combination of results from different laboratories re mains difficult to support. Calibration to the U.S. Reference Pertussi s Antisera appears to have been successful at standardizing the result s in some laboratories, Statistical analyses are affected by assay pre cision and are not necessarily reliable sole predictors of biologicall y relevant differences in quantitative results. If results from differ ent laboratories must be compared, appropriate studies of precision an d quantitative agreement should be conducted to support the specific c omparisons.