Color Doppler Ultrasound for the Diagnosis of Sacroiliitis in Inflammatory Back Pain

Color Doppler ultrasound may represent an appropriate tool for the diagnosis of sacroiliitis in patients presenting with inflammatory back pain.

Color Doppler ultrasound (CDUS) may represent an appropriate tool for the diagnosis of sacroiliitis in patients presenting with inflammatory back pain (IBP), according to a study published in The Journal of Rheumatology.

Sacroiliitis is a chief hallmark of spondyloarthritis (SpA) and its radiographic identification is part of the diagnosis and monitoring of inflammatory back pain. Early diagnosis and treatment of SpA is essential in order to prevent permanent damage and dysfunction. Investigators sought to determine the diagnostic value of CDUS for this condition, comparing it with magnetic resonance imaging (MRI) (used as the gold standard).

Adult patients with IBP and suspected axial SpA were enrolled in a prospective cross-sectional interventional study and compared with control patients with confirmed axial SpA as assessed by MRI. All study participants underwent MRI and CDUS of the sacroiliac joint in the same week, along with a clinical examination to assess disease activity. In the study, 2 rheumatologists blinded to all patient data read the CDUS images and 1 rheumatologist read the axial MRIs. Diagnostic properties of CDUS were analyzed at both the joint and patient levels, and sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) for sacroiliitis diagnosis were calculated.

A total of 99 patients (mean age, 39.8; 61.6% men; median disease duration, 24 months) were included in the analysis. There were 36 participants (83% men; P =.001) with established axial SpA in the control group.

CDUS had a sensitivity of 60% (95% CI, 49-70%), specificity of 93% (95% CI, 88-98%), PPV of 83% (95% CI, 78-95%), and NPV of 43% (95% CI, 33-56%) at the joint level. At the patient level, sensitivity was 63% (95% CI, 48.7-75.7%), specificity was 89% (95% CI, 76-96%), PPV was 87.2% (95% CI, 72.6-95.7%), and NPV was 66.7% (95% CI, 53.3-78.3%).

CDUS had a sensitivity of 54% (95% CI, 36.6-71.2%), specificity of 82% (95% CI, 63.1-93.9%), PPV of 79% (95% CI, 57.8-92.9%), and NPV of 59% (95% CI, 42.1-74.4%) for the diagnosis of axial SpA.

These results suggest that the less expensive CDUS should be used for screening, while MRI should be reserved for confirmation of positive cases of CDUS.

Study limitations include performance of MRI and CDUS on different days and a cross-sectional design.

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“CDUS largely used for assessment of peripheral arthritis and enthesitis in [spondyloarthritis] could also be a practical and useful tool for the diagnosis of active sacroiliitis in patients with IBP,” concluded the authors. They recommended that future research involve larger patient cohorts.

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Rosa JE, Ruta S, Bravo M, et al. Value of color Doppler ultrasound assessment of sacroiliac joints in patients with inflammatory low back pain [published online December 15, 2018]. J Rheumatol. doi:10.3899/jrheum.180550