[The re-evaluation of 140 patients diagnosed as ankylosing spondylitis and nonradiographic axial spondyloarthritis].

Objective: To re-evaluate the diagnoses of ankylosing spondylitis (AS) and nonradiographic axial spondyloarthritis (nr-axSpA) and analyze the incidence and reason of misdiagnosis.
Methods: Patients who were previously diagnosed as AS and nr-axSpA before referrals to Peking Union Medical College Hospital (PUMCH) were re-evaluated by three rheumatologists of PUMCH according to the modified New York criteria for AS and Assessment of SpondyloArthritis international Society (ASAS) axial SpA classification criteria for nr-axSpA.
Results: Totally 87 prior AS patients and 53 prior nr-axSpA patients were enrolled in this study. After re-evaluation, 57 patients were still diagnosed as AS and 16 patients were still diagnosed as nr-axSpA. The misdiagnosis incidences were 34.48% and 69.81%, respectively. The misdiagnosis incidence of nr-axSpA was higher than that of AS (P < 0.01).
Conclusions: The misdiagnosis of AS were mainly due to the misjudgment of sacroiliac joints by CT. The misdiagnosis of nr-axSpA were mainly due to the misjudgment of sacroiliac joints by magnetic resonance imaging. Moreover, the misuse of ASAS axial SpA classification criteria contributed to the misdiagnosis also.