Background: Chemical agents such as tannic acid and detergents have been shown to introduce non-random bias in allergen measurement.
Objective: We investigated how several substances that are commonly found in floor dust (carpet fresheners, powdered pesticides, and table salt) affected immunoassays of purified standard allergens.
Methods: Three sets of experiments were conducted to: (1) screen for interference with allergen enzyme-linked immunosorbent assay (ELISA); (2) test for concentration-response; and (3) assess the site-of-action of a given dust additive (i.e. the effect on allergen binding to primary or secondary antibody). The ELISAs are commercially available two-site monoclonal antibody assays for Der p 1, Der f 1, and Fel d 1, and a monoclonal/polyclonal assay for Bla g 1. Outcomes are reported in terms of reaction rate (colour change per unit time), which is directly proportional to the amount of bound allergen.
Results: In the initial screening experiments, carpet fresheners tended to decrease Der p 1 assay reaction rates, increase Der f 1 assay rates, and produce little change in Fel d 1 assay rates. Three carpet fresheners decreased Der p 1 assay rate responses in a concentration-dependent manner. Two carpet fresheners noticeably increased Der f 1 assay reaction rates in both the screening and the concentration-response tests. Powdered pesticides increased reaction rates in the Bla g 1 assays and increased the slope of the dilution curve compared with that of the purified allergen. Salt decreased the reaction rates of Bla g 1 assays at allergen concentrations greater than 0.01 U/mL. For each of the four allergens, the largest effects of dust additives occurred when secondary antibody binding was altered.
Conclusions: Some common household dust components can introduce systematic error into immunoassays for arthropod allergens.