Association between Leeds Dactylitis Index and ultrasonographic features: a multicentre study on psoriatic hand dactylitis

Objectives: The aim of this study was to explore the link between specific sonographic findings and Leeds Dactylitis Index basic (LDI-b) score in psoriatic arthritis (PsA) patients with hand dactylitis. Methods: Ninety-one hand dactylitis were evaluated in a multicentre study for the presence of pain, functional limitation and tenderness (2-point scale) and LDI-b score. Dactylitic fingers were investigated using high-frequency US in grey scale (GS) and power Doppler (PD). According to median LDI-b score value of 12, fingers were then divided into two groups and categorised into quartiles on the basis of the value of ratio of circumference. Results: Dactylitic fingers with a LDI-b score >12 showed a significantly higher prevalence of GS flexor tenosynovitis (p=0.015), PD flexor tenosynovitis (p=0.001) and soft tissue oedema (p=0.004), when compared with those with those with LDI-b score <12. GS synovitis at proximal interphalangeal (PIP) level (p=0.003) showed more frequent in dactylitic fingers with a LDI-b score <12, than those with a higher LDI-b value. Fingers in the fourth quartile showed a significantly higher prevalence of GS flexor tenosynovitis of grade ≥2 (p=0.046) and joint synovitis of grade ≥2 at PIP level (p=0.028). Conclusions: We found that high values of LDI are associated with US flexor tenosynovitis and soft tissue oedema in PsA dactylitis. Results suggest a potential role of PIP joint synovitis in the genesis of hand digital swelling and of extra-articular structures alterations in determining the LDI score.