Low yield for extended reading of patch tests with topical corticosteroids

Background. On the basis of reports that up to 30% of patch-test reactions are missed if an extended reading is not performed, we required that patients who were being patch-tested with the corticosteroid series return for a reading at least 1 week after placement of the allergens. Objective: To report our institutional experience with extended readings (day 7 or beyond) of patch-test reactions to the corticosteroid series. Methods: We retrospectively reviewed patch-test reactions to corticosteroids since extended readings were implemented (April 2001 to June 2004). Results: A total of 135 patients were patch-tested with 1,656 corticosteroid allergens. On day 5, five patients had five positive patch-test reactions; by the time of the extended reading, no new reactions had developed in these patients. Of the patients with no reactions on day 5, two had a positive result at the extended reading: each had a relevant reaction to budesonide 0.1%, one on day 7 and the other on day 9. Conclusions: Only 2 reactions (to 1,656 corticosteroids) became apparent at the extended reading. Extended readings were of limited value in our experience.