Is the severity of initial sensitization to diphenylcyclopropenone in alopecia areata patients predictive of the final clinical response?

Immunotherapy by diphenylcyclopropenone (DPCP) is generally started with 2% DPCP sensitization, however in recent years studies have questioned the necessity of sensitization that may cause patients severe reactions and troubles at the onset of therapy. The purpose of the present study was to evaluate the association between the severity of initial reaction to 2% DPCP sensitization in AA patients and clinical response. In this retrospective study, 110 AA patients who continued therapy for at least 6 months were enrolled. Hair loss and hair regrowth rates were calculated based on the Severity of Alopecia Tool (SALT) scoring system. Initial reaction to 2% DPCP sensitization after 2 weeks was graded as negative reaction (absence of any reaction), doubtful reaction (mild erythema, pruritus, and irritation for minutes after test), weak (erythema, mild edema, and scaling), and strong to extreme reaction (vesicles, bullae, ulcer, and discharge). The degrees of the initial reaction to 2% DPCP after 2 weeks were negative reaction 13 (11.81%), doubtful reaction 40 (36.36%), weak reaction 33 (30%), and strong to extreme reaction 24 (21.81%). Patients were divided into two groups: (A) patients with less than 12-month therapy (75 of 110), (B) patients with more than 12-month therapy (35 of 110). Initial reaction to 2% DPCP sensitization was not correlated with hair regrowth rate in either group (group A: Spearman's rho = 0.194, p = 0.095; group B: Spearman's rho = 0.063 p = 0.720). After 12-month treatment with DPCP, hair regrowth rate was significantly greater than 6-months therapy (group A: 17.03 ± 37.78, group B: 49.26 ± 36.34; p = 0.003). The severity of hair loss at the onset of treatment was significantly associated with the response rate in both groups (p-value <0.002). Based on our results, it is the initial severity of the disease and not the initial reaction to 2% DPCP sensitization that predicts the clinical response to DPCP immunotherapy.