Clinical, Investigative and Therapeutic assessment of patients with positive versus negative Autologous Serum Skin Test (ASST) in chronic urticaria at a tertiary care hospital

Abstract

Background Chronic urticaria (CU) has prevalence of 0.1%-3%. About 30-50% of patients with chronic spontaneous urticaria (CSU) have an autoimmune etiology, called as chronic autoimmune urticaria (CAU). These patients usually demonstrate wheal and flare response to intradermal injection of autologous serum. Objective To compare clinical, investigative manifestations and therapeutic response in patients with positive versus negative ASST in patients of CSU. Materials and Methods This was prospective comparative study comprising 45 CSU patients of age group 18-65 years, attending outpatient department of dermatology during a period of 2 years. Patients were subjected to ASST, complete blood count, urine routine examination, thyroid stimulating hormone, serum vitamin B12 levels and random blood sugar. All the patients were treated according to EAACI/GA2LEN/EDF/WAO 2013 guidelines and were followed up for a period of 90 days. Results ASST was positive in 57.77% and negative in 42.22% of the patients. Significant association of ASST positivity was seen with longer duration, generalized distribution, angioedema and partial or no response to treatment. Whereas, shorter duration, localised disease and association with dermographism was significantly higher in ASST negative patients. Conclusion ASST is a simple, cost effective screening test for detecting CAU patients. This test has good sensitivity and so can be used as a predictive clinical test to diagnose auto immune urticaria which is more likely to have longer, more widespread and severe disease and more likely to require higher doses of antihistamines and longer duration of treatment.