Abstract: Objective To evaluate the consistency of psoriasis-involved body surface area （BSA） measurement among raters from different clinical centers after training in a new standard operating procedure （SOP） for involved BSA measurement, so as to provide a method for the evaluation of psoriasis with high accuracy and operability. Methods Firstly, two raters from Guangdong Provincial Hospital of Chinese Medicine（GPHCM） independently and alternately assessed the disease severity in 40 patients with psoriasis after systematic training in the BSA-SOP. Then, one of the raters from GPHCM and 11 raters from 11 subcenters separately assessed the disease severity in 209 patients with psoriasis by using the BSA-SOP, and the consistency was evaluated by using intraclass correlation coefficient （ICC）. Results There was a very high degree of consistency in involved BSA values between the 2 raters from GPHCM （ICC = 0.989, 95% confidence interval: 0.979 - 0.994）. The consistency of involved BSA values for the assessment of psoriasis severity was also high among the rater from GPHCM and the raters from 11 subcenters （ICC ranging from 0.849 to 0.998）. Conclusion The raters from different centers showed high consistency of involved BSA measurement for the assessment of psoriasis severity after training in the new BSA-SOP, so the BSA-SOP can serve as a reliable reference for multicenter clinical studies.

Key words: Psoriasis, Severity of illness index, Body surface area, Consistency