Significance-prevalence index number: A reinterpretation and enhancement of data from the North American Contact Dermatitis Group

Background: The North American Contact Dermatitis group (NACDG) periodicall y reports allergen reaction rates and clinical significance. These results are not formally interpreted combining both components into one index. Objective: The put-pose of this study is to introduce the Significance-Prev alence Index Number (SPIN), which is a parameter that assesses the relative importance of different allergens. Methods: Data was collected from published studies reported by NACDG from 1 984 through 1996. The SPIN for each tested allergen was calculated as the p roduct of the proportion of the population allergic by the weighted clinici an-assessed likelihood of relevance of the reaction. Results: In the studies done in 1992 through 1996, fragrance mix, quaterniu m-15, balsam Peru, formaldehyde, thiuram mix, nickel sulfate, neomycin, bac itracin, carba mix, and paraphenylenediamine were the 10 leading allergens in clinical importance as measured by SPIN. Our SPIN calculations suggest t hat ethylenediamine and benzocaine have markedly decreased in clinical impo rtance over the past decade, whereas methylchloroisothiazoline/methylisothi azolinone has become a leading allergen. A number of allergens demonstrate high to intermediate SPIN, yet are not included in the T.R.U.E. test. These clinically important allergens include bacitracin, diazolidinyl urea, glyc eryl thioglycate, ethyleneurea melamine-formaldehyde, and imidazolidinyl ur ea. Conclusion: SPIN allows clinicians to incorporate both the allergenicity an d the relevance of the allergen into one measure.