Narvaez J et al. – The authors observed significant differences in the magnetic resonance imaging (MRI) findings of the hand and wrist that can help to distinguish between rheumatoid arthritis (RA) and psoriatic arthritis (PsA) in the early stages of disease. This imaging method could help to assist in the differential diagnostic process in selected patients in whom diagnosis cannot be unequivocally established after conventional clinical, biochemical, and radiographic examinations.Methods
- Twenty early RA and 17 early PsA patients with symptomatic involvement of the wrist and hand joints and inconclusive radiographic studies were examined prospectively with contrast–enhanced MRI.
- Images were evaluated in accordance with the Outcome Measures in Rheumatology Clinical Trials recommendations.
- Certain MRI features, such as the presence of enthesitis or extensive diaphyseal bone marrow edema, were observed exclusively in PsA (P = 0.0001).
- These distinctive findings were present in nearly 71% (12/17) of PsA patients.
- Diffuse and, in some cases, pronounced soft–tissue edema spreading to the subcutis was also seen more frequently in patients with PsA (P = 0.002).
- There were no significant differences in the frequency of synovitis, bone erosions, subchondral bone edema, or tenosynovitis between the 2 groups.
- However, in RA extensor tendons were involved more often than the flexor tendons, whereas in PsA the opposite was observed (P = 0.014).
- With respect to the discriminatory power of the different MRI findings examined, only the presence of enthesitis or diaphyseal bone edema and, to a lesser extent, the pattern of hand tendon involvement and the presence of soft–tissue edema accurately differentiated PsA from RA (all these features achieved accuracies greater than 0.70).