Patch test results in psoriasis patients on biologics

The objective of this study was to determine the prevalence of positive patch tests in patients with psoriasis receiving biologics and whether these results differ from those of patients with psoriasis not on biologics.

An institutional review board-approved retrospective chart review was conducted for patients with psoriasis patch tested January 2002-2012 at Tufts Medical Center. Patients had a history of psoriasis, psoriatic arthritis, and patch testing as identified by International Classification of Diseases, Ninth Revision codes 696.1, 696.0, and 95044, respectively, in their records. Patients were tested to a modified North American Contact Dermatitis Group standard and cosmetics series. Readings were performed at 48 hours and 72 to 96 hours. The North American Contact Dermatitis Group grading system was used to grade reactions.

Fifteen patients with psoriasis on biologics (cases) and 16 patients with psoriasis not on biologics (control subjects) were studied. The biologics used were ustekinumab (n = 7), etanercept (n = 4), adalimumab (n = 3), and infliximab (n = 1). Eighty percent (12/15) of cases had at least 1 positive reaction compared with 81% (13/16) of the control subjects; 67% (10/15) of cases had 2+ reactions compared with 63% (10/16) of the control subjects, and 27% (4/15) of cases had 3+ reactions, compared with 38% (6/16) of control subjects. These differences were not statistically significant.

Given the limitation of small numbers of patients, biologics do not appear to influence the abilities of patients with psoriasis to mount a positive patch test.