Extended diagnostic value of autologous serum skin test and basophil CD63 expression assay in chronic urticaria

B.I. and E.G. contributed equally to this work. Funding sources: this work was supported by Hungarian research grants (OTKA K81381, TÁMOP 4·2·2/B‐10/1‐2010‐0024). Conflicts of interest: none to declare. Madam, Chronic urticaria (CU) is characterized by the occurrence of widespread, short‐lived weals, appearing daily or almost daily for at least 6 weeks.1 There has been strong evidence supporting an autoimmune basis of the disease in approximately 27–50% of patients with CU, who have functional autoantibodies against the high‐affinity IgE receptor and/or IgE.1 A correct diagnosis of autoimmune CU (ACU) is difficult but important because of the presence of more severe clinical symptoms. Currently, the autologous serum skin test (ASST) serves as a screening method, after which more adequate confirmation is gained through functional assays, to identify the ACU group.2 The basophil histamine release assay and flow cytometric basophil activation tests (BAT) are considered to be the gold standards; however, these tests are not accessible on an outpatient basis.3, 4 ASST is normally performed using undiluted autologous patient sera.5 To avoid nonspecific results in ASST, a 1 : 10 serum dilution has been suggested.6 Our goal was to investigate whether ASST using diluted instead of undiluted sera would enhance specificity and to detect any correlation between the degree of basophil CD63 expression and clinical severity of the ACU.