Ultrasonography of Inflammatory and Structural Lesions in Hand Osteoarthritis: An OMERACT Agreement and Reliability Study

Objective: To standardize and assess the reliability of ultrasonographic assessment of inflammatory and structural lesions in patients with hand osteoarthritis (OA). Methods: The Outcome Measures in Rheumatology (OMERACT) Ultrasound Working Group selected synovial hypertrophy (SH), joint effusion (JE), and power Doppler (PD) signals as the main inflammatory lesions in hand OA, and suggested osteophytes in the scapho-trapezio-trapezoid (STT) and cartilage defects in the proximal interphalangeal (PIP) joints as novel additions to previous structural scoring systems. A complementary imaging atlas provided detailed examples of the scores. A reliability exercise of static images was performed for the inflammatory features, followed by a patient-based exercise with six sonographers testing inflammatory and structural features in twelve hand OA patients. We used Cohen's kappa (κ) for intra-reader and Light's κ for inter-reader reliability for all features except PD, in which Prevalence-Adjusted Bias-Adjusted Kappa (PABAK) was applied. Percentage agreement was also assessed. Results: The web-based reliability exercise demonstrated substantial intra- and inter-reader reliability for all inflammatory features (κ>0.64). In the patient-based exercise, intra- and inter-reader reliability varied: SH κ=0.73 and 0.45; JE κ=0.70 and 0.55; PD PABAK=0.90 and 0.88; PIP cartilage κ=0.56 and 0.45; STT osteophytes κ=0.62 and 0.36. Percentage close agreement was high for all features (>85%). Conclusion: With ultrasound, substantial to excellent intra-reader reliability was found for inflammatory features of hand OA. Inter-reader reliability was moderate, but overall high close agreement between readers suggest that better reliability is achievable after further training. Assessment of osteophytes in the STT joint and cartilage in the PIP joints achieved less good reliability and the latter is not endorsed. Keywords: Hand osteoarthritis; outcome measures; ultrasonography.