CHARACTERIZATION OF SKIN PRICK TESTING RESPONSES FOR DETECTING SENSITIZATION TO DETERGENT ENZYMES AT EXTREME DILUTIONS - INABILITY OF THE RAST TO DETECT LIGHTLY SENSITIZED INDIVIDUALS

We observed that a group of detergent enzyme workers with known exposu re to the subtilisin enzyme, Alcalase (Novo Industries, Bagsvaerde, De nmark), exhibited percutaneous sensitivity to Savinase (Novo Industrie s), a microbial protease, to which there was no previous occupational exposure. This was attributed to either cross-reactivity between these enzymes or to foreign enzyme contaminants contained in the Savinase a ntigen. The aims of this study were to determine the range of concentr ations eliciting percutaneous responses to Alcalase and to another enz yme, Rapidase (an alpha-amylase) (Gist Brocades, Belgie, Netherlands); to compare the sensitivity of RAST and skin prick testing; and to cha racterize the relationship between wheal site and antigen concentratio n. Prick resting was conducted over six log(10) antigen dilutions of A lcalase and Rapidase in 30 workers with previous exposure and skin rea ctivity to enzymes (group 1) and compared to nonexposed control groups , which included 60 atopic subjects (group 2) and 30 nonatopic subject s (group 3). The RAST was performed with Alcalase and Rapidase antigen s. The percutaneous threshold concentrations in group 1 subjects varie d widely from 10(3) to 10(-3) mu g of protein per milliliter. Of 19 gr oup 1 workers with skin test reactivity to Alcalase, 84% had positive RAST results; 83% of 24 workers who were reactive to Rapidase had posi tive RAST results. It was concluded that skin prick testing is preferr ed over in vitro methods for longitudinal monitoring of human sensitiz ation to workplace allergens. In addition, the data predicted that bas ed on a known Alcalase level of 0.07% in Savinase, 26% of Alcalase-sen sitized subjects could react to Savinase. An excellent correlation (r > 0.97) was found between log concentration of antigen and wheal size parameters, with the log diameter and log area performing equally as w ell (r > 0.98). Analysis of variance revealed that more than 60% of in tragroup variation represented human variability in wheal parameters a t each concentration tested whereas at least 95% of intergroup variati on was due to regression. The excellent correlations of both wheal dia meter and area with antigen concentrations were attributed to the very small changes observed between test concentrations.