A substantial proportion of patients with chronic spontaneous urticaria (CSU) are refractory to antihistamines. However, identifying the subpopulation whose urticaria is not completely controlled by antihistamines remains difficult. The response of autologous serum skin test (ASST), a clinical test for the detection of basophil histamine-releasing activity upon autoantibodies or autoreactive stimulation, has been suggested as a potential predictor in the control of urticaria. We sought to identify proteins that were differentially expressed in the sera of patients with positive and negative ASST results and to investigate their association with urticaria control.Proteomics analysis was performed using sera from 3 CSU patients with positive ASST results compared with those showing negative ASST results. Seven upregulated and 5 downregulated proteins were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry in the ASST-positive group compared with the ASST-negative group.Proteins that were differentially expressed according to the ASST results in CSU patients were classified into 6 groups: apolipoproteins, glycoproteins, modified albumin, haptoglobulin, plectin, and others. Among these, apolipoprotein J or clusterin was validated using an enzyme-linked immunosorbent assay. Clusterin levels in 69 ASST-positive patients were significantly higher than those in 69 ASST-negative patients and in 86 healthy controls (231.2 ± 44.0 vs 210.2 ± 36.1 vs 118.7 ± 71.9 μg/mL, P < 0.001). Furthermore, clusterin levels differed significantly between patients with responsive and refractory responses to antihistamine treatment within 3 months (231.0 ± 39.1 vs 205.1 ± 40.4 μg/mL, P < 0.001). ASST results and serum clusterin levels can predict 92.7% of CSU patients whose urticaria would be refractory to antihistamines. Serum clusterin can be a prognostic marker to determine the responsiveness to antihistamine treatment in patients with CSU.