Comparative study of patch test using traditional method vs. prior skin abrading.

ABSTRACT

BACKGROUND: The patch test is an essential procedure for the investigation of aetiologic diagnosis of allergic contact dermatitis, although it is not yet able to fully reproduce the events of the initial site of contact with the allergen. OBJECTIVES: The aims of the present study are (i) to assess whether removal of the superficial corneous layer results in test positivity differences vs. the traditional technique, (ii) to assess the probable and/or possible and past and/or present sensitivity and relevance for each method, and (iii) to compare specific relevance of nickel sulphate for each method. RESULTS: Concordance of positive reactions was 75.9% (66 of 87), with 21.8% (19 of 87) positivity results on the abraded side only and 2.3% (2 of 87) on the unabraded side (P < 0.05). Concordance of the substances with probable and/or possible and past and/or present relevance was 77.3% (58 of 75) for the abraded side and 21.3% (16 of 75) and 1.3% (1 of 75) for the unabraded side (P < 0.05). Analysis of isolated relevance for nickel sulphate showed 95.6% (22 of 23) concordance. CONCLUSIONS: (i) We found a greater number of positive substances on the abraded side, and when only the 2 + and 3 + reactions were considered, greater relative discordance was also observed; (ii) relevance analysis revealed a statistically significant difference between the two methods; (iii) differences in nickel sulphate test positivity and relevance for the two methods did not reach statistical significance.