Psoriatic arthritis spondylitis radiology index: a modified index for radiologic assessment of axial involvement in psoriatic arthritis

OBJECTIVE: To develop and validate a modified index for assessing the radiologic axial involvement in psoriatic arthritis (PsA) in a group of patients with established disease. METHODS: Patients were included on clinical and/or radiologic criteria. The modified index combined features of existing radiologic indices for ankylosing spondylitis (AS) with the addition of scores for the facet joints of the cervical and lumbar regions. Scores for the BathAS Radiology Index (BASRI), the modified Stoke AS Scoring System (mSASSS), and the new index were obtained from current radiographs. The construct validity of the new index was assessed by examining the correlation with patient reported outcomes, such as the Revised Leeds Disability Questionnaire (RLDQ) and BathAS Functional Index (BASFI), and anthropometric measures. RESULTS: Radiographs were available for 73 patients (54 men, 19 women, mean age 49.4 +/- 11.0 yrs, mean disease duration 14.0 +/- 7.9 yrs). Due to difficulty in visualizing and interpreting the lumbar facet joints, only the cervical facet joints were included in the new score, called the PsA Spondylitis Radiology Index (PASRI). Overall, the PASRI resulted in less missing data than the mSASSS, but had less complete data than the BASRI. The PASRI also had fewer zero scores than the mSASSS and the score range for the PASRI exceeded that of the mSASSS and the BASRI. Correlation with anthropometric and patient reported outcomes was good for both the PASRI and BASRI, with both these measures outscoring the mSASSS. CONCLUSION: The PASRI encompasses a greater range of the spinal radiologic features of PsA, provides a greater score range and fewer zero scores, and correlates well with anthropometric and patient reported measures. PMID: 19332625 DOI: 10.3899/jrheum.080491