The autologous serum skin test in a cohort of chronic idiopathic urticaria patients compared to respiratory allergy patients and healthy individuals

BACKGROUND: A positive autologous serum skin test (ASST) is considered to reflect the presence of anti-FceRI and/or anti-IgE autoantibodies that are capable of activating mast and basophil cell degranulation. The ASST is regarded as a reliable in vivo test in chronic idiopathic urticaria (CIU) patients, with diagnostic, therapeutic and prognostic implications. However, positive ASST results have also occasionally been demonstrated in patients with other diseases and in healthy subjects. OBJECTIVE: To evaluate the specificity and sensitivity of the ASST in a cohort of CIU patients compared to a cohort of respiratory-allergic patients and a group of normal individuals. METHODS: ASST was performed in a cohort of 116 subjects, 47 subjects with seasonal allergic rhinitis, 32 respiratory-symptom-free CIU patients, and 37 healthy individuals. RESULTS: The results were compared statistically to those of the CIU patients. The intradermal injection of autologous serum induced a weal and flare reaction in 17/32 (53.1%) CIU patients; 14/47 (29.8%) patients with seasonal allergic rhinitis (P=0.06) and in 15/37 (40.5%) of the healthy controls (P=0.34). The sensitivity and specificity of the ASST in the CIU patients and the seasonal allergic rhinitis patients was 53 and 28%, respectively. When comparing the CIU patients with the healthy controls the sensitivity and specificity was 55 and 31%, respectively. The positive and negative predictive values of the ASST when comparing CIU patients with healthy controls were 53 and 59.5%, respectively. The positive and negative predictive values of the ASST in the CIU patients compared to seasonal allergic rhinitis patients were 53 and 70%, respectively. CONCLUSION: The relatively low sensitivity and specificity of the ASST in the CIU patients compared to the seasonal allergic rhinitis patients and healthy controls warrants a more critical interpretation of the ASST in chronic idiopathic urticaria.