Prevalence of distal interphalangeal joint ultrasonography features in psoriatic arthritis, skin psoriasis, osteoarthritis and healthy individuals: a cross-sectional study

Background: Distal interphalangeal (DIP) joint involvement is a feature of both psoriatic arthritis (PsA) and hand osteoarthritis (OA), and nail-changes are features seen both in PsA and nail psoriasis patients without joint involvement (PsO). In both PsA and OA, ultrasonography (US) is used to quantify DIP joint inflammation.Objectives: To explore disease-specific US-detected characteristics in the DIP-joints and extensor tendon entheses in patients with DIP-joint OA, PsA, PsO with nail involvement, and healthy controls (HC).Methods: In PsA, PsO, OA and HC US examination of DIP joints 2-5 and the extensor tendon were performed. The US images were scored for DIP joint grey-scale synovitis, DIP joint Doppler, osteophytes and erosions (grade 0-3) and presence/absence of enthesitis and peritendonitis of the extensor tendon according to OMERACT standards. Prevalences were calculated on all included fingers (i.e. four fingers per participant), and differences in prevalences were tested using Chi-square statistics.Results: Fifty PsA patients (44% females; mean age: 55y), 13 PsO patients (38% females; mean age 54y), 12 OA patients (100% females, mean age 71y), and 29 HC (52% females, mean age 48y) participated. The prevalences across the diagnosis groups are shown in figure 1, and the distribution of US outcomes was significantly different (highest Chi-square P-value: 0.0127). The PsA group had the largest prevalence of extensor tendon enthesitis (45.5%), peritendonitis (15%), and DIP joint erosions (11%), but also exhibited a considerable prevalence of osteophytes (46%). In the PsO group, the most marked findings were synovitis (33%) and enthesitis (35%). The OA group had the largest prevalence of DIP joint synovitis (67%) and osteophytes (88%) but also 25% prevalence of enthesitis. 24% of the HC group had a grade 1 synovitis.Conclusion: This cross-sectional study found significant patterns of US findings distributed dependent on the underlying condition. PsA patients were mainly differentiated by the presence of extensor tendon enthesitis and peritendonitis. A high prevalence of enthesitis and synovitis was seen in patients with DIP joint OA. The high prevalence of enthesitis in PsO is consistent with a preclinical phase of PsA in this group.Disclosure of Interests: Jørgen Guldberg-Møller Speakers bureau: Novartis, Ely Lilly, AbbVie, BK Ultrasound, Marius Henriksen: None declared, Mikael Boesen Speakers bureau: Image Analysis Group, AbbVie, AstraZeneca, Eli Lilly, Esaote, Glenmark, Novartis, Pfizer, UCB, Lene Dreyer: None declared, Karen Ellegaard: None declared, Marie Skougaard: None declared, Christine Ballegaard: None declared, Ai Lyn Tan: None declared, Richard Wakefield Speakers bureau: Novartis, Janssen, GE, Lars Erik Kristensen Consultant of: UCB Pharma (Advisory Board), Sannofi (Advisory Board), Abbvie (Advisory Board), Biogen (Advisory Board), Speakers bureau: AbbVie, Amgen, Biogen, Bristol-Myers Squibb,Celgene, Eli Lilly, Gilead, Forward Pharma, Janssen Pharmaceuticals, MSD, Novartis, Pfizer, and UCB Pharma