Value of Color Doppler Ultrasound Assessment of Sacroiliac Joints in Patients with Inflammatory Low Back Pain.

To evaluate the diagnostic value of color Doppler ultrasound (CDUS) for the detection of sacroiliitis, in patients with inflammatory back pain (IBP). Consecutive patients with IBP and suspected axial spondyloarthritis (SpA), but without a definitive diagnosis, were included. Consecutive patients with defined SpA and axial involvement were included as a control group. All patients underwent clinical evaluation, magnetic resonance imaging (MRI), and CDUS of sacroiliac joints (SIJ) within the same week. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) for the diagnosis of sacroiliitis by CDUS were calculated, using MRI as the gold standard. There were 198 SIJ evaluated in 99 patients (36 with previous SpA). There were 61 men (61.6%), with a mean age of 39.8 years (SD 11.3) and median disease duration of 24 months (IQR 12-84). At the patient level, CDUS had a sensitivity of 63% (95% CI 48.7-75.7%) and a specificity of 89% (95% CI 76-96%). The PPV was 87.2% (95% CI 72.6-95.7%) and the NPV was 66.7% (95% CI 53.3-78.3%). At joint level, CDUS had a sensitivity of 60% (95% CI 49-70%) and a specificity of 93% (95% CI 88-98%). The PPV was 83% (95% CI 78-95%) and the NPV was 43% (95% CI 33-56%). The sensitivity of CDUS for the diagnosis of axial SpA was 54% (95% CI 36.6-71.2%), specificity was 82% (95% CI 63.1-93.9%), PPV was 79% (95% CI 57.8-92.9%), and NPV was 59% (95% CI 42.1-74.4%). CDUS showed adequate diagnostic properties for detection of sacroiliitis and is a useful tool in patients with IBP.