Computed tomography scanning facilitates the diagnosis of sacroiliitis in patients with suspected spondylarthritis: results of a prospective multicenter French cohort study

Arthritis Rheum. 2012 May;64(5):1412-9. doi: 10.1002/art.33466.


Objective: To assess the performance of computed tomography (CT) scanning for ascertaining sacroiliitis in patients with suspected spondylarthritis (SpA).

Methods: The Echography in Spondylarthritis French cohort consists of 489 patients with suspected SpA. At baseline, all patients underwent clinical examination, HLA-B typing, and pelvic radiography. Pelvic CT scanning was performed if sacroiliitis on radiography was considered uncertain or if patients presented with buttock pain duration of >6 months. A set of 100 paired radiographs and CT scans was read in a blinded manner by 2 radiologists, and the kappa coefficient was used to assess their interreader reliability. One of the radiologists read the 173 available pairs of radiographs and CT scans performed at baseline.

Results: After training, interreader reliability was moderate for sacroiliitis grading on radiographs (κ = 0.59), excellent on CT scans (κ = 0.91), and excellent for ascertaining sacroiliitis on both radiographs (κ = 1) and CT scans (κ = 0.96). The first and second readers considered the quality of imaging to be excellent in 66% and 67%, respectively, of the radiographs (κ = 0.88) and in 93% and 92%, respectively, of the CT scans (κ = 0.93). Concordance between radiographs and CT scans was low for sacroiliitis grading (κ = 0.08) or ascertainment (κ = 0.16). Definite sacroiliitis was ascertained on radiographs in 6 patients (3.5%) (confirmed by CT scans in 4 patients) and on CT scans in 32 patients (18.5%). A history of uveitis was associated with definite sacroiliitis on radiographs (P = 0.04) and CT scans (P < 0.0001).

Conclusion: Definite sacroiliitis was underestimated by radiography, as compared to CT scanning. CT scanning should facilitate the diagnosis of ankylosing spondylitis in patients with suspected SpA.

Trial registration: NCT00794404.

Publication types

  • Clinical Trial
  • Multicenter Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Cross-Sectional Studies
  • Female
  • Humans
  • Male
  • Observer Variation
  • Outpatients
  • Pelvis / diagnostic imaging
  • Prospective Studies
  • Reproducibility of Results
  • Sacroiliitis / complications
  • Sacroiliitis / diagnosis*
  • Sacroiliitis / diagnostic imaging
  • Single-Blind Method
  • Spondylitis, Ankylosing / complications
  • Spondylitis, Ankylosing / diagnosis*
  • Spondylitis, Ankylosing / diagnostic imaging
  • Tomography, X-Ray Computed / methods*

Associated data