COMPARISON OF A RADIOALLERGOSORBENT (RAST) INHIBITION METHOD AND A MONOCLONAL ENZYME-LINKED-IMMUNOSORBENT-ASSAY (ELISA) FOR AEROALLERGEN MEASUREMENT

Background Mouse and rat urinary proteins are potent occupational alle rgens for exposed personnel. Methods of measuring airborne allergens d iffer greatly, and reported levels of allergens vary considerably betw een laboratories. Objectives To compare the values obtained using two different methods of allergen detection. Methods Air samples were coll ected in rat rooms in Sweden and the United Kingdom at 2L/min on to po lytetrafluoroethylene (PTFE) filters and extracted in buffer containin g 0.5% v/v Tween 20. Airborne rat urinary allergen (RUA) was measured in all samples by both RAST inhibition using a polyclonal human serum pool (UK) and a two monoclonal antibody sandwich ELISA employing antib odies specific for Rat n 1.02 (alpha(2u)-globulin) (Sweden). Results T he two methods gave values which were correlated (r(2) log values = 0. 72, P < 0.0001), but differed by several orders of magnitude (median [ range] ratio of RAST inhibition/ELISA = 316 [7-26(80)] There was a sys tematic bias: as the absolute values increased, the difference in the measurements increased. The rat urine standards used were antigenicall y similar. Conclusions A large contrast in RUA values obtained from th e two assays was observed in this study. This may be primarily due to methodological differences, but variations in antibody specificities o r composition of allergenic epitopes in the air samples may contribute . The results demonstrate that standardization of methods and antibodi es is necessary before interlaboratory comparisons can be made.