The radiological assessment of axial involvement in psoriatic arthritis: a validation study of the BASRI total and the modified SASSS scoring methods.

OBJECTIVES To assess the validity of the BASRI and m-SASSS scores for the radiological axial involvement in psoriatic arthritis (PsA). Secondary end-points were to report on clinical, functional and radiographic characteristics of axial involvement. METHODS Inclusion criteria were satisfaction of the CASPAR criteria and the presence of clinical, functional and/or radiological axial involvement. Three observers scored the radiographs by BASRI and m-SASSS. The construct validity was assessed by examining the correlation of instruments with patient reported outcomes and anthropometric measures. The reliability and the feasibility of the scores were also considered. RESULTS Seventy-seven patients were enrolled (58 M, 19 F, mean age 49.4 + or - 10.8 yrs, disease duration 13.9 + or - 7.9 yrs). Both instruments showed some modest but significant correlation with clinical measures. When compared, the BASRI showed a correlation with BASMI (rho=0.47, p<0.001), cervical rotation (rho=-0.49, p<0.001), tragus to wall (rho=0.34, p<0.01) and occiput to wall (rho=0.49, p<0.001), modified Schober test (rho=-0.24, p<0.05) and RLDQ (rho=-0.24, p<0.05). When compared, m-SASSS showed a correlation with BASMI (rho=0.39, p<0.001), cervical rotation (rho=-0.41, p<0.001), tragus to wall (rho=0.31, p<0.01) and occiput to wall (rho=0.42, p<0.001), modified Schober and Schober test (rho=-0.34, p<0.001; rho= -0.32, p<0.01), finger to floor (rho=0.37, p<0.01). No correlation was found with BASFI, BASDAI and HAQ. Test-retest showed a good reliability of the scores. Both were feasible but BASRI was the quickest. CONCLUSION Our results showed that BASRI and m-SASSS were valid instruments for use in spondylitis associated with psoriatic arthritis. Longitudinal data is required to provide sensitivity to change of the two scores.