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FRI0125 Impact of Repeating Imaging of the Sacro-Iliac Joints over One Year on the Classification According the ASAS Axial SPA Criteria of Patients
  1. P. Bakker,
  2. M. de Hooge,
  3. R. van den Berg,
  4. F. van Gaalen,
  5. M. Reijnierse,
  6. T. Huizinga,
  7. D. van der Heijde
  1. Leiden University Medical Center, Leiden, Netherlands

Abstract

Background It is known that in axial spondyloarthritis (axSpA) inflammatory lesions on MRI of the SI joints (MRI-SI) can change over time. The usefulness of repeating imaging in the diagnostic process is unclear.

Objectives To investigate how patients with short-term chronic back pain are classified by the ASAS axSpA- criteria at baseline and after 1 year follow-up, with a focus on the role of imaging.

Methods Patients in the SPACE cohort (back pain: ≥3 months, ≤2 years, onset <45 years) with (suspicion of) axSpA underwent MRI and X-rays of the sacroiliac joints at baseline and 1 year follow-up. Only patients with complete MRI- and X-SI data at both baseline and year 1 were included in the analysis (n=80). MRI-SI and X-SI were scored independently by 3 well-calibrated readers according to the ASAS definition for a positive MRI and the mNY-criteria. Readers were blinded for patient characteristics and time sequence. Fulfillment of ASAS or mNY criteria was considered positive if 2/3 readers agreed. For each timepoint, patients were classified according the ASAS axSpA criteria and grouped in different arms (imaging arm: mNY+/- or MRI+/-; clinical arm, fulfillment of both arms and possible axSpA). In contrary to the normal application of the criteria, where a positive feature remains positive, we grouped patients according to the finding at one year, ignoring previous imaging findings.

Results At baseline, 41/80 patients (32.8%) fulfilled the ASAS criteria (clinical arm: 22; imaging arm: 12, both arms: 7) (table). After 1 year, 3 additional patients fulfilled the criteria (2 clinical arm; 1 imaging arm). After 1 year, in 5 patients MRI-SI became positive and 1 patient fulfilled the mNY criteria. On the other hand, MRI-SI became negative after 1 year in 4 other patients. Of these patients, 3 still fulfilled the ASAS criteria (imaging arm (mNY+, n=1) or clinical arm (n=2)). Only 1 patient (classified as axSpA at baseline) would be missed if imaging would have been performed at 1 year only (due to a negative MRI).

Conclusions With one year longer symptom duration, 3/39 (8%) of the possible SpA patients could be classified additionally as axSpA because of additional SpA features (5%) or positive MRI (3%), while 1/41 (2%) of the axSpA patients would not be classified due to a normal MRI. There was a switch between imaging and clinical arm in 12% of the patients. Therefore, our data show the robustness of the axSpA criteria and does not support repeating imaging after one year.

Disclosure of Interest None declared

DOI 10.1136/annrheumdis-2014-eular.1630

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