Background Despite the interest in validating ultrasound (US) as an outcome measure in rheumatology, progress has been achieved only in defining the pathological US abnormalities associated with rheumatoid arthritis (RA). A recent review of US studies in osteoarthritis (OA) showed very limited data about hand OA (1). Patients with OA have been previously described as having synovial thickening (SH), erosions, osteophytes and rarely positive Power Doppler (PD) signal on US examination (2). These findings suggest a possible overlap between US features of hand OA and RA.
Objectives This study aimed to investigate the usefulness of a standardised US examination protocol for hand joints in differentiating subclinical RA from OA, in patients with equivocal clinical examination. In addition, we explored which simplified hand US scores perform better for every disease taken separately.
Methods A retrospective, observational study was conducted in patients with inflammatory hand joint pains referred to the US clinic with suspected subclinical inflammation. We compared patients with established RA (n=224) and hand OA (n=73), with respect of several demographic, clinical, laboratory and US parameters. We used a 22 hand joint US examination protocol (wrists, metacarpophalangeal and proximal interphalangeal joints bilaterally - OMERACT scoring system) for all patients, and compared it with a range of smaller, pre-defined US joint scores.
Results Significant statistical differences were found for age at the time of scan, US parameters and clinical examination between the two groups. Subclinical joint inflammation in the context of equivocal clinical examination was found in 9.6% OA patients compared to 46.4% in RA (p<0.05). The comparison between several joint scores in OA patients suggested that for detecting subclinical inflammation, multiple finger joints should be examined (20 joint score, comprising MCPs and PIPs was significantly more informative than the 12, 10 and 4 joint scores, (p<0.05)), whereas in RA, the 4 joint scores (assessing wrists and MCP 5 or MCP 2 and 3 bilaterally) detected inflammation just as well as the 22 joint score (p<0.05).
Conclusions Our study findings reflected differences between the incidence and characteristics of subclinical inflammation in patients with RA and OA. The attractiveness of using US scores assessing a smaller number of joints may pose limitations, despite being of benefit in a time-constrained clinical setting. Our study assessed comparatively the utility of several US hand scores, however, further research is need to validate their use in practice.
Keen HI, Wakefield RJ, Conaghan PG. A systematic review of ultrasonography in osteoarthritis. Annals of the rheumatic diseases. 2009;68(5):611–9.
Vlychou M, Koutroumpas A, Malizos K, Sakkas LI. Ultrasonographic evidence of inflammation is frequent in hands of patients with erosive osteoarthritis. Osteoarthritis and cartilage/OARS, Osteoarthritis Research Society. 2009;17(10):1283–7.
Disclosure of Interest None declared