STATISTICAL EVALUATION OF THE PERSISTENCE OF ACQUIRED HYPERSENSITIVITY BY STANDARDIZED PATCH TESTS

Numerous studies have focused attention on the influence of various bi ological and environmental factors on contact hypersensitivity. In ord er to evaluate the persistence and/or modification of allergic contact sensitivity to a number of common contact sensitizers, the same stand ardized patch tests were repeated on 174 subjects with contact sensiti vity after a time lapse of 5 years (1987-1992). In 18.4% of the cases, 1 or more sensitivities were lost; 28.7% of the patients had a higher number of positive patch tests after 5 years, while the remaining 52. 9% of the patients showed no change in the number of positive patch te sts. In 88%, the positive allergens were unchanged, whereas in the rem aining 22% of the subjects, they showed 1 or more variations. The asso ciation between the allergens most often positive was calculated for b oth the 1st and the 2nd patch test results. Moreover, to evaluate the frequency of an allergen's positivity, we studied the disappearance of old sensitivities and the appearance of new sensitivities by the McNe mar test. Cobalt chloride was the only allergen with a significant fre quency of new positivities over the period of observation (p<0.01). Lo gistic regression analysis was performed to evaluate the possible infl uence of positive tests to other allergens, and of some clinical findi ngs associated with contact dermatitis, on the sensitivity to cobalt c hloride in 1987 and in 1992.