Ultrasound as a Useful Tool in the Diagnosis of Rheumatoid Arthritis in Patients With Undifferentiated Arthritis.

Background: Nowadays, rheumatologists face challenges in finding an effective method to classify and treat patients with undifferentiated arthritis (UA). There is a need for new tools that could ensure accurate characterization of inflammatory processes in these patients.
Objective: The aim of this study was to investigate if a characterization of UA patients using ultrasound (US) may help to fulfill the 2010 American College of Rheumatology/European League Against Rheumatism (ACR/EULAR) rheumatoid arthritis (RA) classification criteria in a real-life cohort.
Methods: We conducted a cross-sectional study in 2 rheumatology care clinics. Patients not fulfilling the 2010 ACR/EULAR RA criteria were included. On the examination day, all patients underwent a physical examination, radiography, and US. The 7-joint US score was adopted to scan all patients. The US was performed according to EULAR criteria and interpreted by Outcome Measures in Rheumatology definitions. Gray-scale and power Doppler synovitis and tenosynovitis were scored. Bone erosions were also evaluated during the US examination.
Results: A total of 204 patients were included. The diagnosis was modified from UA to RA in 86 patients (42.1%). Also, the final score of the 2010 ACR/EULAR RA classification criteria changed from a mean of 4.6 to 6.5 after the US examination. In addition to synovitis, a wide range of tenosynovitis and bone erosions were detected by US. Synovitis was more frequently detected in second metacarpophalangeal joint followed by second metatarsophalangeal joint (MTPj) and fifth MTPj. The tendons of the wrist and second and third fingers were the most affected. In relation to bone erosions, second metacarpophalangeal joint and fifth MTPj were the joints with more proportion of anatomical damage.
Conclusions: The US demonstrated to be useful to help accurately classify as RA patients previously diagnosed with UA.