Evaluation of peripheral enthesitis in spondyloarthritis: Ultrasonography versus clinical examination

Background: Enthesitis is an important feature of spondyloarthritis but may often be subclinical. Data is sparse, especially from India, on the ultrasonography (USG) detection of enthesitis in these patients. The present study aimed to find the prevalence and pattern of entheseal involvement assessed clinically and by USG. Methods: Fifty-two spondyloarthritis, 26 rheumatoid arthritis, and 26 healthy controls were evaluated for enthesitis by clinical examination and by USG using 2014 OMERACT consensus group definitions at bilateral Achilles insertion on the calcaneus, plantar fascia attachment on the calcaneus, quadriceps tendon insertion on the patella, patellar tendon origin from the inferior pole of the patella, and patellar tendon insertion on the tibial tuberosity. At least one ultrasonographic finding at any of the above sites was considered positive for enthesitis. Results: The number of entheseal sites screened in spondyloarthritis patients was 520 and 260 each in rheumatoid arthritis and healthy controls. USG (sensitivity - 94.2%) was better in detecting enthesitis than clinical examination (sensitivity - 69.2%). Clinical examination was highly specific (100%) compared to USG (55.7%) in differentiating from rheumatoid arthritis and healthy controls. USG alone without clinical findings was positive at 23.8% of sites while clinical examination alone without USG findings was positive at 5.2% of sites. Frequency of enthesitis in rheumatoid arthritis was not more than healthy controls (6.1% vs. 8.1%, respectively) and was much less than spondyloarthritis (34%). Conclusion: USG is a good screening tool for detection of enthesitis but cannot replace clinical examination completely