The effects of carpet fresheners and other additives on the behaviour of indoor allergen assays

Background Chemical agents such as tannic acid and detergents have been sho wn 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) affect ed immunoassays of purified standard allergens. Methods Three sets of experiments were conducted to: (1) screen for interfe rence 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 antib ody), The ELISAs are commercially available two-site monoclonal antibody as says for Der p 1, Der f 1, and Fel d 1, and a monoclonal/polyclonal assay f or 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 aller gen. Results in. the initial screening experiments, carpet fresheners tended to decrease Der p 1 assay reaction rates, increase Der f 1 assay rates, and pr oduce little change in Fel d 1 assay rates. Three carpet fresheners decreas ed Der p 1 assay rate responses in a concentration-dependent manner. Two ca rpet fresheners noticeably increased Der f 1 assay reaction rates in both t he screening and the concentration-response tests. Powdered pesticides incr eased reaction rates in the Bla g 1 assays and increased the slope of the d ilution curve compared with that of the purified allergen. Salt decreased t he 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 add itives occurred when secondary antibody binding was altered. Conclusions Some common household dust components can introduce systematic error into immunoassays for arthropod allergens.