Usefulness of ultrasound as a predictor of elderly-onset rheumatoid arthritis with polymyalgia rheumatica-like onset

Objectives Differentiation between polymyalgia rheumatica (PMR) and elderly-onset rheumatoid arthritis (EORA), especially in elderly patients, is often difficult due to similarities in symptoms and serological kinetics. In this study, we aimed to analyse the predictors of EORA with PMR-like onset. Methods Seventy-two patients diagnosed with PMR, who attended our hospital for routine care and underwent musculoskeletal ultrasonography at that time were evaluated. Synovitis was evaluated semi-quantitatively (0-3) by grey scale (GS) and power Doppler (PD) in 24 joints [both hands (wrist, metacarpophalageal, and proximal interphalangeal joints) and both shoulder joints]. Results Overall, 18 patients had rheumatoid arthritis (25.0%); the mean age was 75.0 years, and 34.7% and 65.3% were male and female, respectively. In PMR and PMR/EORA groups, multivariate logistic analysis showed that rheumatoid factor positivity, GS >= 2 of hand joints, and PD >= 1 of hand joints were independent factors with significant differences. At least one of the three factors had a sensitivity of 88.9% and specificity of 92.6%. Conclusions The presence of at least one of the criteria: rheumatoid factor positivity, GS >= 2, and PD >= 1 of hand joints, suggested the possibility of developing EORA within 1 year of PMR diagnosis.