Objective: To determine the prevalence and compare the results of positive autologous serum skin test (ASST) and autologous plasma skin test (APST) in Thai chronic urticaria patients.

Material and Method: A retrospective review of all chronic urticaria patients attending the Urticaria Clinic who underwent ASST and APST between January 2010 and March 2014 was conducted. The data on their demography, disease severity, and results of ASST, APST, and other relevant tests were collected and analyzed using a statistical software.

Results: Seventy-nine patients, comprising 14 (17.7%) males and 65 (82.3%) females, were included in the present study. Their median (range) age was 37 years (18 to 73 years). The median (range) duration of the disease was two years (2 months to 30 years). ASST was positive in 48 patients (60.8%) whereas APST was positive in 50 patients (63.3%). The difference in prevalence between both tests was not statistically significant (p = 0.593). A statistically significant association with higher number of wheals during each attack of urticarial symptoms was found in ASST-positive group (p<0.001), but not in APST-positive group (p = 0.064).

Conclusion: ASST and APST can similarly detect autoreactivity in Thai chronic urticaria patients. Thus APST, the less established test between the two, is unnecessary.

Keywords: Autoimmune urticaria, Autologous plasma skin test, Autologous serum skin test, Chronic urticaria, Skin test