Patient-rated angioedema severity using a novel photo-aid for predicting non-mast cell mediator-induced angioedema diagnosis.

Background: Patients with non-mast cell mediator-induced angioedema (NM-AE) usually experience a diagnostic delay. Therefore, a clinical tool for predicting NM-AE diagnosis is essential.

Objective: To identify clinical predictors related to a confirmed diagnosis of NM-AE.

Methods: Participants with a history of recurrent AE with unknown causes were enrolled. They were classified into mast cell mediator-induced AE (M-AE) and NM-AE according to the response to anti-mast cell mediator therapy. All participants were asked to rate their worst AE ever experienced (% Photomax) from 0 to 100% using a novel photo aid. Clinical characteristics were recorded and analyzed by univariable and multivariable analysis.

Results: Thirty-five participants were included, 25 with NM-AE and 10 with M-AE. AE located at extremities, face, and genitalia and positive family history were significantly associated with NM-AE. The AE severity in the NM-AE group was significantly higher than in the M-AE group, with the mean % Photomax of 82.4 ± 20.3 vs 47.5 ± 25.6 (p < 0.001), respectively. Univariable analysis showed that the % Photomax (every 10% increase), feet AE and hands AE were predictive of being NM-AE with the area under the receiver operating characteristic curve (AuROC) of 0.87 (95% CI 0.75, 0.99), 0.85 (95% CI 0.72, 0.98), and 0.84 (0.69, 0.99), respectively. Multivariable analysis showed that the combination of hands AE and % Photomax enhanced diagnostic accuracy (AuROC 0.94, 95% CI 0.86, 1.0) and constituted the prototype formula for calculating the diagnostic probability.

Conclusion: Patient-rated angioedema severity using a novel photo aid combined with hands AE had a high probability of diagnosing NM-AE.