Fig. 1

Overview of the development of the mSASSS prediction model. The known and potential factors affecting the radiographic progression were included in the formulation of the GLM or ANN model (blue box). Treatment-dependent variables include the elapsed time after baseline evaluation, time-integrated CRP levels, and exposure to TNF inhibitors. Baseline mSASSS was modified into two formats and assigned to the models (red and yellow box): (1) C-spine and L-spine mSASSS and (2) number of each score of mSASSS (0, 1, 2, and 3). Target outcome was the mSASSS at follow-up. Finally, two models were built by the formats of mSASSS and separately evaluated. ANN, artificial neural network; ASDAS, Ankylosing Spondylitis Disease Activity Score; CRP, c-reactive protein; C-spine, cervical spine; GLM, generalized linear model; L-spine, lumbar spine; mSASSS, modified Stoke Ankylosing Spondylitis Spinal Score; NSAID, non-steroidal anti-inflammatory drug; TNF, tumor necrosis factor