AB1107 DACTYLITIS IN PSORIATIC ARTHRITIS – PREVALENCE AND RELIABILITY OF ULTRASOUND PATHOLOGIES
Authors: S. Kamp Felbo, M. Ǿstergaard, I. J. Sørensen, L. Terslev
Journal: Annals of the Rheumatic Diseases (2020)

Background: Dactylitis is an important clinical feature in psoriatic arthritis (PsA). Early imaging studies indicated tenosynovitis and adjacent subcutaneous edema (SCE) as the main components in dactylitis, but more recent ultrasound (US) studies have found involvement of many other structures including synovitis and enthesitis (1). To date, there is no consensus on which US elementary lesions constitutes dactylitis. Objectives: To investigate by US the prevalence of different elementary lesions found in dactylitis in PsA, and the reliability of scoring these lesions in a clinical setting. Methods: In a cross-sectional study 31 patients with PsA and dactylitis were included from a rheumatology out-patient clinic. The most affected digit in each patient was examined both dorsal and volar, in longitudinal and transversal plane, using greyscale (GS) and color Doppler (CD) US with a 6-15 MHz linear transducer. One examiner scanned all patients and a 2nd examiner scanned 10 patients for inter-reader reliability. 1st examiner re-read images after appr. 3 weeks for intra-reader reliability. Following pathologies were scored: 1. SCE (hypo- or anechoic areas in the subcutaneous tissue, with/without hyperemia) 2. Soft tissue thickening 3. Synovitis of the metacarpophalangeal (MCP) or metatarsophalangeal (MTP), proximal interphalangeal (PIP), distal interphalangeal (DIP) or interphalangeal (IP) joints 4. Tenosynovitis of the flexor tendon and 5. Enthesitis at the deep flexor tendon (FT) and the extensor tendon (ET) entheses 6. Paratenonitis of the ET (hypoechoic area and CD around the ET). OMERACT US definitions and scoring were used for synovitis, tenosynovitis and enthesitis. Results: Patients were 55% males, with short disease duration (median (interquartile range (IQR)) 1(0-6) year) and moderate disease activity (median (IQR) DAS28 3.2(2.4-4.5). 45% of the examined digits were fingers, 55% toes. 74% were tender, 26% non-tender. US findings and intra- and inter-reader agreements are presented in table 1. Intra- and inter-reader agreements were moderate to excellent, except for some entheses due to low prevalence of findings. Therefore, the prevalence and bias adjusted Kappa was used for these. All pathologies were found primarily in combinations, most commonly SCE and synovitis (71%), followed by SCE and flexor tenosynovitis (52%), and all three in combination (52%). No patient had flexor tenosynovitis as a sole component. No significant difference was found in tender vs. non-tender dactylitis. Table 1. US findings and intra/inter-reader agreement using different Kappa statistics $ GS +/- GS 0-3 CD +/- CD 0-3 n (%) K* grade K** n (%) K* grade K** Subcutaneous edema 23 (74) 1 / 1 17 (55) 0.8 / 0.7 Soft tissue thickening 25 (81) 1 / 1 Flexor tenosynovitis 16 (51) 0.9 / 1 2 (2-2) 0.9 / 0.9 14 (45) 0.9 / 1 2 (2-3) 1 / 0.9 Synovitis K* K** K* K** MCP/MTP 21 (68) 0.9 / 0.6 2 (1-2) 1 / 0.5 5 (16) 1 / 1 2 (2-2) 1 / 1 PIP (n=27) 15 (56) 1 /0.7 2 (1-3) 1 / 0.7 9 (33) 0.9 / 0.5 2 (2-2) 1 / 0.7 DIP/IP 19 (61) 0.9 / 1 2 (2-3) 0.9 / 0.9 9 (29) 0.8 /1 2 (2-2) 0.9 / 1 Enthesitis Any sign Inflammatory^ Structural’ K# K# K# Deep flexor tendon 14 (47) 0.7 / 0.6 11 (36) 0.8 /0.7 12 (39) 0.8 / 0.7 Extensor tendon PIP (n=27) 14 (52) 0.6 / 0.3 12 (39) 0.8 / 0.5 6 (22) 0.9 / 0.8 Extensor tendon DIP/IP 9 (29) 0.9 / 0.4 8 (26) 1 / 0.7 7 (23) 0.9 / 0.8 GS + CD K* Paratenonitis 10 (32) 0.7 / 0.4 Values are prevalence (n (%)) and grade (median (IQR)). $: Cohen’s Kappa (K*) or PABAK (K#) for binary outcomes, weighted Kappa (K**) (squared weights) for continuous outcomes. GS: Greyscale, CD: Color Doppler ^Inflammatory: Thickened, hypoechogenic or CD activity. ‘Structural: Enthesophytes/calcifications or erosions. Conclusion: In this US study dactylitis in PsA was found to represent several pathologies, most often subcutaneous changes in combination with synovitis and/or flexor tenosynovitis. Reliability of scoring pathologies of dactylitis in a clinical setting is overall good. References: [1]Bakewell, J Rheumatol, 2013 Disclosure of Interests: Sara Kamp Felbo Grant/research support from: Celgene, Mikkel Ǿstergaard Grant/research support from: AbbVie, Bristol-Myers Squibb, Celgene, Merck, and Novartis, Consultant of: AbbVie, Bristol-Myers Squibb, Boehringer Ingelheim, Celgene, Eli Lilly, Hospira, Janssen, Merck, Novartis, Novo Nordisk, Orion, Pfizer, Regeneron, Roche, Sandoz, Sanofi, and UCB, Speakers bureau: AbbVie, Bristol-Myers Squibb, Boehringer Ingelheim, Celgene, Eli Lilly, Hospira, Janssen, Merck, Novartis, Novo Nordisk, Orion, Pfizer, Regeneron, Roche, Sandoz, Sanofi, and UCB, Inge Juul Sørensen: None declared, Lene Terslev Speakers bureau: LT declares speakers fees from Roche, MSD, BMS, Pfizer, AbbVie, Novartis, and Janssen.