Clinical relevance of tixocortol pivalate-positive patch tests and questionable bioequivalence of different hydrocortisone preparations

Background. Tixocortol-21-pivalate (tixocortol pivalate) is used as a surrogate marker for contact allergy to hydrocortisone and other corticosteroids. Objective. To review the results of repeated open application testing (ROAT) and patch testing with hydrocortisone creams and ointments in tixocortol pivalate patch test-positive patients. Methods. ROAT was performed when the history of hydrocortisone contact dermatitis was negative or equivocal. Hydrocortisone cream and/or ointment patch tests were performed in patients with and without histories of hydrocortisone contact dermatitis. Results were excluded in patients allergic to vehicle ingredients. Results. ROAT was positive in 15 of 20 patients (75%) with hydrocortisone cream versus 6 of 16 (38%) with hydrocortisone ointment (p = 0.02). Patch testing was positive with hydrocortisone cream in 23 of 27 patients (85%) versus 1 of 14 (7%) with hydrocortisone ointment (p < 0.0001). Only 1 of 26 tixocortol pivalate patch test-negative patients had a positive patch test with hydrocortisone cream caused by a vehicle ingredient. Conclusions. Clinical relevance was shown in most patients with positive tixocortol pivalate patch tests. Hydrocortisone creams gave positive patch tests and positive repeated open application tests much more often than hydrocortisone ointments. There were also significant differences in patch test reactivity among different hydrocortisone creams. We hypothesize that these differences may be explained by differences in hydrocortisone transepidermal penetration in different vehicles.