[False positive reaction in measurement of allergen-specific IgE--comparison of 3M IgE FAST-Plus Test using polystyrene well as adsorbent with Phadezym RAST].

Irrelevant IgE binding to cellulose discs is known to give false positive results in Phadezym RAST (Pharmacia) for the estimation of allergen-specific IgE in serum. We investigated FAST-Plus Test (3M Diagnostic Systems), an enzyme-linked sandwich type Fluoro-Allergo-Sorbent Test in which a particular allergen was coated to polystyrene well. Phadezym RAST and CAP RAST (Pharmacia) using cellulose-derivative discs as adsorbent were used as reference methods. Patients' sera which gave negative blank reactions to uncoated filter paper disc in the Phadezym RAST system were assayed for specific IgE to 6 allergens using FAST-Plus Test, CAP RAST and Phadezym RAST, and the results of the former two were compared with those of Phadezym RAST using a comparable class system. FAST-Plus Test showed variable correlations with Phadezym RAST, the correlation coefficients ranged from 0.41 to 0.97 (r = 0.462 in house dust 1, r = 0.713 in house dust 2, r = 0.412 in Candida albicans, r = 0.952 in Dermatophagoides peteronyssinus, r = 0.969 in Dermatophagoides farinae and r = 0.682 in Japanese cedar), although most of the results were within one class difference. Similar correlations were obtained between CAP RAST and Phadezym RAST. Of 3004 patients' sera tested in the past two years using Phadezym RAST, 132 (96 cases) displayed positive blank reactions to the uncoated filter paper disc. Of the 96 cases, 80 sera were assayed for binding of IgE to the uncoated cellulose-derivative disc in the CAP RAST system. 18 showed positive results up to 7 IU/ml.(ABSTRACT TRUNCATED AT 250 WORDS)