Reliability of Radiographic Scoring Methods in Axial Psoriatic Arthritis

Abstract

Important differences exist between axial psoriatic arthritis (AxPsA) and ankylosing spondylitis (AS). The Bath Ankylosing Spondylitis Radiology Index (BASRI), the modified Stoke Ankylosing Spondylitis Spinal Score (mSASSS), and the Radiographic Ankylosing Spondylitis Spinal Score (RASSS) were developed to score AS, and the Psoriatic Arthritis Spondylitis Radiology Index (PASRI) to score AxPsA. We aimed to develop a computerized scoring application and compare the intra- and interrater reliability of these scoring systems in AS and AxPsA. A computerized scoring application was developed to facilitate the scoring of radiographic features and calculate total scores for established scoring methods for AS and AxPsA. Digital spinal radiographs of 18 patients with AS and 40 patients with AxPsA were read in random order individually by 4 rheumatologists, data were entered into the application, and scores were obtained. The intraclass correlation coefficients (ICC) of the intra- and interrater reliability of scores for each method were then computed. In AS, the intra- and interrater ICC was 0.91 and 0.80 for sacroiliitis grade, 0.96 and 0.86 for BASRI-spine, 0.98 and 0.86 for mSASSS, 0.96 and 0.75 for RASSS, and 0.99 and 0.93 for PASRI, respectively. In AxPsA, the intra- and interrater ICC was 0.81 and 0.67 for sacroiliitis grade, 0.77 and 0.52 for BASRI-spine, 0.91 and 0.65 for mSASSS, 0.90 and 0.68 for RASSS, and 0.92 and 0.88 for PASRI, respectively. Available radiographic scoring systems perform well in AS and have moderate intra- and interrater reliability when applied to AxPsA. However, PASRI may be superior for assessing structural damage in AxPsA.