INTERLABORATORY STUDY EVALUATING QUANTITATION OF ANTIBODIES TO HAEMOPHILUS-INFLUENZAE TYPE-B POLYSACCHARIDE BY ENZYME-LINKED-IMMUNOSORBENT-ASSAY

An interlaboratory study was conducted to determine whether an enzyme- linked immunosorbent assay (ELISA) with an antigen preparation compose d of various-sized fragments of Haemophilus influenzae type b polysacc haride conjugated to human serum albumin could be standardized across laboratories and whether the ELISA-derived results from different labo ratories are equivalent to those obtained by the standard radioactive antigen binding assay (RABA) for quantitation of anti-H, influenza typ e b polysaccharide antibodies. Twenty coded human serum samples were q nantitated by ELISA in 11 laboratories and by RABA in 5 laboratories. The mean RABA-derived values served as the basis for all comparisons. While the overall correspondence of antibody values between the two me thods was good, significant differences were found among some of the 1 1 ELISA data sets and among the mean RABA values. Seven laboratories g enerated higher ELISA antibody values for lo rv-titered sera. Four lab oratories generated antibody concentrations that were not statisticall y different between the two assay methods. The results therefore indic ate that the ELISA can tolerate substantial variations in protocol, su ch as the use of different plates and different antibody reagents, wit hout affecting the quantitation of serum antibodies. However, attentio n should be focused on low-titered sera, as some assay conditions may yield spurious results. This ELISA is a serologic assay which can serv e as an alternative to the RABA for quantitation of antibodies to H. i nfluenzae type b polysaccharide.