How to study inducible urticaria? Development of diagnostic circuits for more than one stimulus

Background: Inducible Urticaria (IU) is a type of Chronic Urticaria (CU) that occurs after exposure to physical and non-physical stimuli The diagnosis is based on patient history and provocation tests, which reproduce the symptoms after exposure to an appropriate triggering stimulus. IU may be present in patients with history of Chronic Spontaneous Urticaria (CSU) Our objective was to establish standardized protocols through diagnostic circuits that included tests for different stimuli in the same visit, reduce consultation time and evaluate their effectiveness and safety. Method: We designed 4 circuits where different test instruments for IU were included: Temptest, Fric-Test, Calibrated Dermographometer, Standard laboratory vortex and suspension of weights (7 kg.) over the shoulder. The circuits were: • Basic Circuit (BC): Dermographism, Temperature (cold and heat), Pressure (delayed an acute) and Vibratory Urticaria (Diagram 1) • Cold Urticaria Circuit (CUC): CB plus Ice Cube Test • Aquagenic Urticaria Circuit (AqUC): CB plus Aquagenic test • Autoimmune Urticaria Circuit (AuUC): CB plus Autologous Serum Skin Test (ASST) Cholinergic Urticaria tests were not included due to COVID pandemic restrictions, nor tests for Solar Urticaria as the necessary technical means were not available. For 6 months, we selected 51 patients with urticaria history lasting for more than 6 weeks. The circuit chosen for the study depended on the initial clinical suspicion. If there was no clear triggering stimulus, the BC was performed which includes the most frequent causes of IU. Results: Of the total number of patients studied, BC was applied to 82.4%, CUC to 7.8%, AqUC to 7.8% and AuUC to 2%. The most frequent diagnosis was Dermographism in 47.05% of the patients. This diagnosis was also present in some patients with CSU. The maximum time to perform these circuits was 30 minutes. None of the patients studied presented systemic reactions, anaphylaxis or other unexpected reactions. Conclusion: We observed that the use of standardized circuits in patients with suspected UI makes it possible to study more than one stimulus and to give the appropriate recommendations in each case. These tests are easy to apply and help to optimize study time. Besides, they allow the detection of physical or non-physical stimuli associated with SCU. Given that no patient presented adverse reactions, it appears to be a safe test. (Figure Presented).