the Quantification of Patch Test Responses: a Comparison Between Echographic and Colorimetric Methods.

Abstract

Patch testing is widely used both for clinical and experimental purposes. Although the clinical grading employed routinely is of practical value;the lack of objectivity makes it unsuitable for research purposes and dose-response analysis studies. Instrumental measuring techniques have been applied to patch test evaluation;because they enable objective quantification of different biophysical aspects of the inflammatory reaction by means of a continuous assessment scale;providing data suitable for statistical analysis. In order to compare the colorimetric and echographic methods for the evaluation of reactions of different intensity;we performed patch tests with 5% nickel sulfate on the flexor aspect of the forearm in 120 nickel-sensitive patients. Clinical and instrumental measurements were performed at 72 h. Numerical values corresponding to instrumental measurements were compared to the positivity degree;as assessed clinically. Whereas echographic parameters;expressing the intensity of oedema and inflammatory infiltration;enabled a distinction between +;+2 and +3 reactions;colorimetric a* values;describing erythema;failed to distinguish between +2 and +3 reactions. Thus;the use of ultrasound is advisable for the quantification of skin reactions of great intensity;whereas the colorimetric method could be usefully employed for dose-response studies assessing minimal eliciting concentrations of allergens;and for the evaluation of clinically undetectable reactions.