There is no consensus regarding the minimum number of joints that should be included in an ultrasound (US) scoring system to reliably assess for disease activity in rheumatoid arthritis (RA).
To assess whether simplified US protocols for hand examination are as informative as the examination of 22 joints in patients with RA, and to correlate the US parameters with disease activity (DAS-28).
This is a cross-sectional study of 224 RA patients stratified based on their DAS-28 scores and assessed using eight preselected US examination protocols, including 22, 18, 16, 14, ten, eight, and two different combinations of four joints, respectively.
We found a significant difference between US hand scores regarding their ability to detect active inflammation and erosions. DAS-28 scores correlated very well with the power Doppler (PD) scores generated by all eight US examination protocols (r = 0.89-1, P < 0.05), irrespective of patients' disease activity. Simplified US scores missed information on presence of PD in 20.6-40.2% patients ( P < 0.05) and misdiagnosed non-erosive hand RA in 12-38.4% patients ( P < 0.05), depending on the number of joints excluded from US hand examination.
Preselected simplified US scores are less reliable in appreciating the disease burden when compared with an extended protocol for 22 joint US examination, raising clinicians' awareness regarding the need to comprehensively assess multiple hand joints to reliably rule out subclinical inflammation.