Development and validation of the spondyloarthritis radiography module for calibration of readers using the modified Stoke Ankylosing Spondylitis Spine Score.

Objective: To develop and validate a reference image module aimed at calibration of readers using the modified Stoke Ankylosing Spondylitis Spine Score (mSASSS) to assess radiographic progression in spondyloarthritis.

Methods: Our working group comprised 6 rheumatologists and 3 musculoskeletal radiologists. The following developmental steps were conducted: (1) review of the literature to identify aspects of the mSASSS requiring methodologic clarity; (2) independent assessment of baseline and 2-year radiographs from 25 patients using the mSASSS (pilot exercise); (3) development of a training module (the Spondyloarthritis Radiography [SPAR] module) that clarifies definitions, rules, and scoring methodology and a set of reference radiographic images; (4) scoring exercise 1 by 6 readers on 39 patients, where baseline and 2-year radiographs were scored blinded to time point; and (5) revision of the SPAR module followed by scoring exercise 2 conducted by the same 6 readers on 35 patients. Reliability of status and 2-year change scores was assessed by the intraclass correlation coefficient (ICC) method.

Results: ICCs for change scores for the radiologist reader pair improved from 0.46 to 0.62 after minimal calibration with the SPAR module. Recalibration from exercise 1 to exercise 2 with the SPAR module led to substantial improvement in interreader reliability for change in mSASSS score from ICC 0.44 (range 0.31-0.62) to ICC 0.62 (range 0.34-0.84). Simultaneous assessment of anteroposterior and lateral lumbar radiographs did not enhance reliability or detection of progression.

Conclusion: Calibration according to the SPAR module led to improved reliability in the scoring of the mSASSS, even for expert readers.