Guideline-recommended inflammatory testing in symptomatic dermographism: a real-world study.

INTRODUCTION

Symptomatic dermographism (SD) is the most common form of chronic inducible urticaria and is increasingly recognized as a burdensome disease. The 2026 international urticaria guideline recommends eliciting dermographism and threshold testing for diagnosis and includes differential blood count and erythrocyte sedimentation rate or C-reactive protein (CRP) as an extended diagnostic work-up in patients with SD. However, the clinical usefulness of these inflammatory tests in SD remains incompletely characterized.

METHODS

In this retrospective real-world cohort study, we examined whether routine inflammatory markers provide interpretable signals in SD, using chronic spontaneous urticaria (CSU) as a reference comparator and serum protein electrophoresis-derived markers, including the inflammatory protein ratio (IPR) ([alpha-1 + alpha-2]/albumin × 100), as exploratory measures of inflammation. We included 726 patients with available serum protein electrophoresis (SPE) data: 579 with CSU only, 107 with SD only, and 40 with both diagnoses. Patients with both CSU and SD were excluded from the primary binary comparison, leaving 686 patients for the main CSU-only versus SD-only analysis.

RESULTS

Compared with CSU, SD showed lower CRP (median [IQR]: 1.40 [0.70-3.30] vs. 2.10 [0.90-5.50] mg/L; p = 0.003) and higher basophil counts (0.04 [0.03-0.05] vs. 0.03 [0.02-0.05] × 109/L; p < 0.001), both of which remained significant after false discovery rate correction. SD patients were younger than CSU patients (39.0 [32.0-49.0] vs. 45.0 [35.0-58.0] years; p = 0.001). In age- and sex-adjusted logistic regression models, higher CRP and lower basophils remained associated with CSU. IPR did not differ significantly between SD and CSU but correlated strongly with CRP in both SD- and CSU-only patients (rho = 0.551 and rho = 0.550, respectively; both p < 0.001).

DISCUSSION: Overall, these results show that some interpretable inflammatory signals are present in SD, but they do not clearly explain why these markers should be measured routinely in SD.