Ankle ultrasound tenosynovitis is a significant predictor of DAS28 – defined rheumatoid arthritis activity

Objective. The study aimed to observe the frequency of ultrasound-defined tenosynovitis in ankle tendon and to evaluate the relationship of ankle tenosynovitis with clinical examination and rheumatoid arthritis (RA) activity measures. Methods. RA patients were recruited in 2018 in the random order of presentation from the out-patient clinic. On the same day of inclusion, all patients underwent clinical examination, laboratory tests (inflammatory markers), ankle ultrasound and patient-reported outcomes. Results. the study included 183 patients with established RA, mostly women (86.3%), with mean age of 57.3 years. The most frequent tenosynovitis was observed in the tibialis posterior tendon (TP; 40.4%), followed by the peroneus longus (23.0%) and peroneus brevis (18.0%) tendons. Compared to patients without TP tenosynovitis, patients with TP tenosynovitis had significantly higher titres of rheumatoid factors (RF; median of 123 IU/mL compared to 64 IU/mL; p = 0.023). Clinically tender (55.2%) and swollen (30.6%) ankles were 4.2 and respectively 11.6 times more likely to reveal tenosynovitis on ultrasound. The presence of ankle tenosynovitis was associated with higher disease activity measures. DAS28 increased proportionally and significantly with the number of ankles with tenosynovitis, the grade of ankle tenosynovitis and power Doppler activity. The absence of ankle tenosynovitis independently and significantly decreased DAS28 with 1.2 points (p < 0.001). Conclusions. the most frequent ankle tenosynovitis observed in RA patients involves the TP tendon, which is associated with higher titres of RF. Swollen ankles are more specific and better predictors of ultrasound-defined ankle tenosynovitis, which has a directly proportional relationship with disease activity in RA. Disease activity scores should include clinical evaluation of ankles and ultrasound information.