Objectives To study the reliability and construct validity of ultrasound in interphalangeal finger joints affected by erosive osteoarthritis (EOA) and non-EOA with MRI as the reference method.
Methods 252 joints were examined by ultrasound, conventional radiography and clinical examination. Ultrasound was performed using a high-frequency linear transducer (12×18 MHz). On the same day, magnetic resonance images of 112 joints were obtained on a 3.0 T magnetic resonance unit. The ultrasound and MRI images were re-read independently by other readers unaware of the diagnosis, clinical and other imaging findings. Interobserver reliability was calculated by the percentage of exact agreement obtained and κ statistics. With MRI as the reference method, the sensitivity and specificity of ultrasound in detecting structural (bone erosions and osteophytes) and soft tissue (effusion and grey-scale synovitis) changes in EOA were calculated.
Results Ultrasound and MRI were found to be more sensitive in detecting erosions than conventional radiography in EOA. A high agreement between ultrasound and MRI in the assessment of bone erosions (77.7%), osteophytes (75.9%) and synovitis (86.5%) was present. A high percentage of inflammatory changes was found in EOA, and in smaller amount in non-EOA, both confirmed by MRI. Good interobserver reliability of ultrasound was obtained for all variables (all median κ >0.8).
Conclusion Grey-scale ultrasound proved to be a reliable and valid imaging technique to assess erosions and soft tissue changes, compared with MRI as a reference method in EOA.
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Funding RW is a research fellow supported by a Ghent University Coordinated Research Initiative (GOA) grant (BOF07/GOA/002).
Competing interests None.
Patient consent Obtained.
Ethics approval This study was conducted with the approval of the University Hospital Ghent, De Pintelaan 185, 9000 Gent, Belgium.
Provenance and peer review Not commissioned; externally peer reviewed.