Agreement Between Clinical Practice and Trained Central Reading in Reading of Sacroiliac Joints on Plain Pelvic Radiographs: Results From the DESIR Cohort

Abstract

Objective. To investigate the degree of agreement between local rheumatologists/radiologists and central trained readers (external standard) on the presence/ absence of sacroiliitis on radiographs of the sacroiliac (SI) joints.Methods. Patients with inflammatory back pain (duration >3 months but <3 years) suggestive of axial spondyloarthritis (SpA) were included in the Devenir des Spondylarthropathies Indifferérenciées Récentes (DESIR) cohort. Baseline radiographs of the SI joints were interpreted by 2 central readers (modified New York criteria); cases of disagreement were adjudicated by a third reader, yielding a positive or a negative result (central reading). The same radiographs were also interpreted by local radiologists/rheumatologists and were rated as "normal," "doubtful sacroiliitis," "obvious sacroiliitis," or "SI joint fusion" (local reading); positive findings were defined as "at least unilateral obvious sacroiliitis," "bilateral obvious sacroiliitis," or "at least unilateral fusion." Agreement and misclassifications between central readers and between central reading versus local reading were calculated (kappa values).Results. Interreader agreement between the central readers was moderate ( ‫؍‬ 0.54); 108 of 688 radiographs (15.7%) were adjudicated. According to local reading ("at least unilateral obvious sacroiliitis"), 183 of the 688 patients (26.6%) had sacroiliitis, whereas according to central reading, 145 of 688 patients (21.1%) had sacroiliitis. Agreement between local reading and central reading was also moderate ( ‫؍‬ 0.55); 76 of 183 patients (41.5%) with "at least unilateral obvious sacroiliitis" (positive by local reading) and 32 of 109 patients (29.4%) with "bilateral obvious sacroiliitis" or "at least unilateral fusion" (positive by local reading) were rated as "negative" by central reading, and 38 of 505 patients (7.5%) and 68 of 579 patients (11.7%), respectively, without sacroiliitis (negative by local reading) were interpreted as "positive" by central reading.

Comparison of MRI with radiography for detecting structural lesions of the sacroiliac joint using CT as standard of reference: results from the SIMACT study

“…Inter-rater agreement about imaging findings was also significantly inferior for radiography compared with both ldCT and MRI, again confirming earlier reports 3. Not surprisingly, T1-weighted MRI was inferior to radiography in the detection of sclerosis.…”

“…However, several investigators have pointed out major problems with the use of radiography for SI joint evaluation. One concern is the large inter-reader variability in the interpretation of SI joint radiographs3 and the failure to improve agreement by training of rheumatologists and radiologists 4. The problems in evaluating radiographs of the SI joints are understandable because pelvic anatomy is complex, the SI joints have an oblique orientation and overlying bowel gas hampers visualisation.…”

Defining active sacroiliitis on MRI for classification of axial spondyloarthritis: update by the ASAS MRI working group

“…Using the DESIR cohort of subjects with inflammatory back pain (IBP) of less than 3 years duration before the age of 50, the reliability of classification of radiographs and MRI was compared between rheumatologists and radiologists of 25 local recruiting centres and central readers 5 7. The results indicate that the existing MRI definition could be applied across multiple centres with the expectation of acceptable reliability and at least with better reliability than the X-ray definition of sacroiliitis according to the modified New York criteria.…”

The term ‘non-radiographic axial spondyloarthritis’ is much more important to classify than to diagnose patients with axial spondyloarthritis

“…Local readers can take into account the clinical characteristics of individual patients when interpreting their imaging studies, especially the potentially important factors of age14 15 or of confounding diagnoses such as erosive osteochondrosis (Modic lesions) at the L4/L5 level. Disagreement in interpreting SIJ imaging, both between local rheumatologists or radiologists and central trained readers and between different central trained readers, has been reported to occur in 20–30% of cases 20 21. The experience in the first randomised controlled trials (RCTs) to study nr-axSpA10 was that the trained central readers revised the interpretation of SIJ radiographs by local readers in 185 (40%) of cases—an unfortunate, but typical, example.…”

“…It is much more important to distinguish between early and established disease based on the duration of symptoms rather than on the absence or presence of structural changes in the SIJ. After 2 years of inflammatory back pain, about 20% of patients with axSpA already have radiographic changes in the SIJ 21 41. Thus, if trials are designed to assess a therapeutic intervention early in the course of the disease, enrolling patients with nr-axSpA will exclude 20–30% who have definitive sacroiliitis in the SIJ—specifically those patients with more aggressive disease.…”