Clinical and Investigative Assessment of Patients with Positive Versus Negative Autologous Serum Skin Test: A Study of 80 South Indian Patients

BACKGROUND: Chronic urticaria (CU) is defined as urticaria persisting daily as or almost daily for more than 6 weeks and affecting 0.1% of the population. Mast cell degranulation and histamine release is of central importance in the pathogenesis of CU. About 40-50% of the patients with chronic idiopathic urticaria demonstrate an immediate wheal and flare response to intra-dermal injected autologous serum. This led to the concept of autoimmune urticaria. AIMS: To determine the occurrence, clinical features, associated clinical conditions, comorbidities of autoimmune urticaria and to compare this with chronic spontaneous urticaria. This study aimed to find the frequency of autologous serum skin test (ASST) positive patients among patients with CU and to identify the clinical and laboratory parameters associated with positive ASST. MATERIALS AND METHODS: Prospective correlation study was done on 80 chronic urticaria patients, more than 6 weeks duration, attending outpatient department of dermatology during a period of November 2007 to January 2010. Patients were subjected to ASST, complete blood count, urine routine examination, liver function tests, renal function tests, thyroid function tests, H. pylori antibody tests, C3 and C4 complement level estimation, antinuclear antibody, and urine analysis. RESULTS: ASST was positive in 58.75% and negative in 41.25% of the patients, respectively. Out of 33 patients with history of angioedema, 9 (27.3%) patients were in ASST negative group and 24 were in positive group, this was statistically significant. Both groups showed no statistically significant difference for epidemiological details. CONCLUSION: ASST is considered a screening test for an autoimmune urticaria, which decreases the rate of diagnosis of “idiopathic” form of chronic urticaria. Patients with an autoimmune urticaria have more severe urticaria, more prolonged duration, more frequent attacks, and angioedema. Identification of autoimmune urticaria may permit the use of an immunotherapy in severe disease unresponsive to anti-histamine therapy.