Figure 1.

Flow chart of study inclusion with patient demographics by HLA-B27 status. χ² tests of t-tests were performed to assess group differences. No significant differences were shown. axSPa, axial spondyloarthritis; BASDAI, Bath Ankylosing Spondylitis Disease Activity Index; BMI, body mass index; CRP, C reactive protein; GESPIC, GErman Spondyloarthritis Inception Cohort; LBP, low back pain; MSD, months of symptom duration; OptiRef, Optimal Referral Strategy for Early Diagnosis of Axial Spondyloarthritis study; SIMACT, SacroIliac joint MRI and CT study; VNC-SWI, Virtual Non-Calcium-Susceptibility Weighted Imaging study.