Good clinical practice in patch testing: readings beyond day 2 are necessary: A confirmatory analysis*1, *2

Background: Despite general recommendations, patch test readings are still sometimes terminated at day 2. Objective: The consequences of failure to read patch tests after day 2 and the influence of exposure time to the patches is quantified. Methods: Patch test data from 9,946 patients with at least one positive reaction at day 2 or later and readings at both days 2 and 3 (from 21,062 patients tested between January 1, 1990, and December 31,...