Whole body MRI in spondyloarthritis (SpA): Preliminary results suggest that DWI outperforms STIR for lesion detection

PurposeTo compare the diagnostic accuracy of DWI and STIR sequences in Whole body (WB) MRI of SpA patients.Materials and methodsTwenty consecutive patients with confirmed active SpA and 20 controls were investigated with identical WB MRI protocols, including DWI and STIR images. Two observers recorded lesions' (high signal intensity foci on STIR and high b-value DWI) in 17 anatomical areas, making a 17-point area score' and a 40-point lesion score'. ROC performance, inter-observer agreement, correlation with clinical parameters and spine and sacro-iliac joints (SIJ) MRI scores were assessed.ResultsSpA patients had significantly higher lesion scores on DWI than on STIR (p<0.025). The lesion score area under the curve was significantly higher with DWI (99.9) than with STIR (95.8, p=0.02). DWI lesion score 5 had both sensitivity and specificity 85 %. With STIR the best threshold 3 yielded sensitivity 85 % and specificity 60 %. DWI area score 3 yielded sensitivity 85 % and specificity 80 %. With STIR the best threshold 4 yielded sensitivity 70 % and specificity 80 %. Inter-observer agreement was strong for both sequences. In patients, the lesion score was positively correlated with ASDAS-CRP, log(CRP), and local MRI scores.ConclusionsDWI is a promising alternative to STIR in WB MRI to detect active SpA lesions.Key Points center dot DWI is a robust alternative to STIR in WBMRI in SpA.center dot DWI might be superior in discriminating relevant inflammatory and degenerative changes.center dot Positive correlations exist between WB MRI, clinical, biological, local MRI data.center dot Distribution and frequency of abnormal MRI findings in SpA are highlighted.