The radiological assessment of axial involvement in psoriatic arthritis

This article summarizes the state of radiological assessment of axial involvement in psoriatic arthritis (PsA). The definition and measurement of axial disease in PsA remain problematic and this situation in turn could affect the choice of approach to evaluate radiological findings of the spine. At present, the radiological assessment has been evaluated by using scoring systems borrowed from ankylosing spondylitis (AS). In particular, the Bath AS Radiology Index (BASRI) and the modified Stoke AS Spine Score (m-SASSS) have been validated for axial PsA. A recent study showed that BASRI and m-SASSS were valid instruments; however, neither score encompassed all radiological features of PsA. Therefore, a new index for assessing radiological axial involvement in PsA was developed--the PsA Spondylitis Radiology Index (PASRI). This new index encompassed a greater range of the spinal radiological features of PsA, providing a greater score range, and it correlated well with anthropometric and patient-reported outcomes. Recently, a study assessed the sensitivity to change of BASRI, m-SASSS, and PASRI, and showed that these 3 instruments provided a moderate sensitivity to change but high specificity to detect the true changes.