An amplified ELISA inhibition method for the measurement of airborne soybean allergens

Background: Measurement of the soybean aeroallergen in Barcelona and other cities where soybean is unloaded is of increasing importance in controlling population exposure and evaluating the influence of such exposure on the p ersistence of asthma symtpoms. Objective: The aims of the study were: (1) t o standardize an amplified ELISA inhibition method for the quantification o f soybean aeroallergen and (2) to compare this method to a previously descr ibed RAST inhibition method. Methods and Results: An amplified competitive ELISA inhibition method with a biotin-streptavidin system was carried out u sing a pool of sera from soybean-sensitized patients. The results were expr essed as U/ml using a low-molecular-mass soybean allergen as reference stan dard. Reproducibility was calculated by statistically comparing the slope o f the regression lines of the standard curve of 4 consecutive assays and by determining the coefficient of variation (CV) of the percent inhibition da ta for each point of several independent sta nda rd curves, each from the s ame assay (intra-assay) and also from a separate assay (inter-assay). No si gnificant differences in the slopes were obtained by analysis of covariance (ANCOVA) F = 1.04. The CV between assays varied between 4 and 22% (for the assay range used in the reference standard) and was greater than the CV wi thin assays (5-10%), Only values with a CV(%) smaller than 20% were conside red acceptable. 78.5% of the samples satisfied this criterion. The RAST inh ibition and ELISA inhibition methods were compared by difference plots from the values of 338 air filter eluates. The intraclass correlation coefficie nt was 0.456 (p < 0.001). After the results of both methods were classified as lower and higher than 165 U/m(3), the kappa index was 0.46 (p < 0.001). Conclusions: The data obtained in the present study are comparable to thos e reported from other similar immunoassays. Moreover, despite the difficult y in comparing air-sampling values from different laboratories, the kappa i ndex may be taken to represent fairly good agreement beyond chance between both methods. All these data demonstrate that the present immunoassay is us eful for measuring airborne soybean aeroallergens and can also be applied t o evaluate the relationship between exposure and the development of asthma symptoms. Copyright (C) 2000 S. Karger AG, Basel.