Decoding the variability in clinical and laboratory profiles of Chronic Inducible Urticaria vs. Chronic Spontaneous Urticaria - a retrospective study from a tertiary care center

Chronic inducible urticaria (CIndU) is characterized by wheals and/or angioedema for longer than 6 weeks induced by specific triggers. The data regarding epidemiology of CIndU is scarce with limited available literature on urticaria severity, investigations, and treatment responses in CIndU compared to CSU. We performed a retrospective chart review of all CIndU patients(cases) enrolled in our Urticaria clinic, past seven years between January 2017 to December 2023. Equal number of CSU patients enrolled during study period were taken as controls. Patients with absence of weals and both CSU and CIndU were excluded from the study. Urticaria severity was assessed by Urticaria activity score over 7 days (UAS7). Statistical analyses were performed using SPSS V29 with P < 0.05 as significant. Out of all records screened, 222 CIndU (cases) and 226 CSU (controls) were eligible based on complete availability of data. Both groups were comparable in terms of age and gender with slight female preponderance. Mean UAS7 at baseline was comparable(p = 0.619) between two groups [(11.49 +/- 10.37 in CIndU vs. 10.9 +/- 12.2 in CSU)]. The mean CRP (mg/dl) levels for CIndU vs. CSU patients was 2.8 +/- 4.2 vs. 6.9 +/- 11.2 (p < 0.001). Serum D-dimer levels (mg/dl) were also significant between cases(167 +/- 220) and controls(265 +/- 452) (p = 0.020). The quality of life assessed by CU-QOL score was 9.39 +/- 9.5 in CIndU vs. 16 +/- 14.8 in CSU (p < 0.001). 80% of CIndU patients and 52% of CSU patients required updosing of antihistamines upto 4 times and the difference was statistically significant between two groups(p = < 0.001). The mean time taken to achieve remission i.e. UAS7 = 0 (T0) was 60 +/- 42 days amongst CIndU while it was shorter in CSU (27.77 +/- 27 days) (p < 0.001).Amongst all CIndU cases, commonest subtypes were symptomatic dermographism (SD) (39.5%) followed by cholinergic urticaria(4.2%) and cold urticaria(1.8%). Our study underscores the distinct clinical and laboratory profiles between CIndU and CSU patients. CIndU patients exhibit poorer response to standard antihistamine doses, requiring more frequent updosing and longer treatment duration. The time to attain remission as assessed by UAS7 score was also longer in CIndU patients than CSU patients (mean difference of 33 days). Further research is warranted to elucidate the underlying mechanisms and explore targeted treatment approaches for CIndU.