Correlation of clinical diagnosis of dactylitis by the dermatologist and ultrasonographic diagnosis by the rheumatologist in patients with psoriasis arthritis: Experience of a single clinic

Background: Dactylitis is a characteristic feature of psoriatic arthritis (PsA). However, early diagnosis of mild dactylitis is challenging and image examination, such as ultrasonography (US), can be helpful. Objectives: We aimed to compare the clinical diagnosis of dactylitis made by the dermatologist and ultrasonographic diagnosis by the rheumatologist. Methods: Consecutive patients diagnosed with peripheral PsA seen in the dermatologic clinics were referred to the same dermatologist for evaluation of dactylitis. Consecutive patients with and without clinical dactylitis were diagnosed in 19 and 19 patients, respectively, by the referred dermatologist. All patients were then referred to an experienced rheumatologist unaware of the clinical diagnosis for sonographic examination of all 20 digits. Dactylitis under US was diagnosed when both proximal and distal parts of a digit were at least 0.25 mm larger than the contralateral digit. Results: For the clinical dactylitis group, 7 (36.8%) patients had more dactylitis diagnosed by US than clinically, and 2 (10.5%) patients had no dactylitis diagnosed by US. For the clinically no dactylitis group, 4 (21.1%) patients had no diagnosis of dactylitis by US, and most of these patients (78.9%) were diagnosed with dactylitis under US by the rheumatologist. More digits affected by dactylitis were found for both groups, although no statistically significant differences were found, probably due to the small sample size. Conclusion: The results revealed concordance between the dermatologist and rheumatologist for clinical dactylitis but not for patients without dactylitis. For PsA patients, US is more sensitive and useful for early dactylitis diagnosis in a dermatologic clinic.