Background Reading of MRIs of the sacroiliac joints (MRI-SI) in clinical trials is usually performed by ≥1 trained readers while in daily practice this is done by local radiologists/rheumatologists. However, this varies in cohorts and in the DEvenir des Spondylarthropathies Indifferenciées Récentes (DESIR)-cohort, MRIs-SI at inclusion were first read by the local radiologist/rheumatologist, then by central readers. The impact of reading by multiple readers in various centres as in daily practice, instead of a centralized reading, is unknown.
Objectives To compare the local reading (LocR) to centralized reading (CentR) regarding the presence or absence of inflammation on MRI-SI.
Methods The 25 participating centers included patients aged 18-50 with inflammatory back pain (IBP; ≥3 months, ≤3 years) in the DESIR-cohort (n=708). Available baseline MRIs-SI were read by local radiologists/rheumatologists with access to clinical and laboratory data, on the presence of inflammatory lesions in both SI-joints. A grade 0 corresponds to “normal”, a grade 1 to “doubtful”, and a grade 2 to “definite inflammatory lesions”. For this analysis, a positive MRI was defined as at least one SI-joint marked grade 2. Next, 2 well-calibrated central readers independently read all MRIs-SI according to the ASAS definition1, blinded for clinical and laboratory data. In case the readers disagreed, an experienced radiologist served as adjudicator. An MRI-SI was marked positive if 2/3 readers agreed.
Agreement between the 2 central readers, between LocR and CentR and between LocR and the central readers separately was calculated (Kappa; % agreement).
Results In this analysis patients with complete MRI-SI data (n=663) were included. Inter reader agreement between the 2 central readers is acceptable (Kappa 0.73), and the percentage agreement (87.5%) is good (table). The adjudicator scored 84/663 (12.7%) MRIs-SI because of disagreement between the 2 central readers. Comparison between CentR (2/3) and LocR shows the same levels of agreement (kappa 0.70, % agreement 86.6%; table). In 38/663 patients (5.7%), the MRI-SI was positive by LocR but negative by CentR; in 51 patients (7.7%) it was the other way around. There was no difference in agreement between LocR and CentR if MRIs-SI were scored by local rheumatologists or by local radiologists (data not shown). Comparisons of LocR versus the separate readers show very similar results (table).
Conclusions Both inter reader agreement between the 2 central readers and agreement between the local and centralized readings is acceptable to good. This indicates that local rheumatologists/radiologists perform as good as trained readers in identifying inflammation on MRI-SI in patients with recent onset IBP, thereby suggesting that MRI-SI is a reliable assessment in diagnosing and classifying the majority of patients with spondyloarthritis.
Rudwaleit ARD 2009;68:1520-7
Disclosure of Interest None declared
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