Peripheral Psoriatic Arthritis: MRI Definitions Of Key Pathologies And Development Of A MRI Scoring System

Title:

Peripheral Psoriatic Arthritis: MRI Definitions Of Key Pathologies And Development Of A MRI Scoring System

Author(s):

M. Østergaard¹, C. Wiell¹, P. Bird², M. Lassere², P. Conaghan³, P. Bøyesen⁴, F. Gandjbakhch⁵, A. Duer-Jensen¹, C. Peterfy⁶, K.g. Hermann⁷, E. Haavardsholm⁴, B. Ejbjerg¹, A. Anandarajah⁸, P. Emery³, H. Genant⁹, F. McQueen¹⁰. ¹Copenhagen Univ, Copenhagen, Denmark; ²NSW Univ, Sydney, Australia; ³Univ Leeds, Leeds, United Kingdom; ⁴Oslo Univ, Oslo, Norway; ⁵Pitié-Salpétrière, Paris, France; ⁶Synarc, San Francisco, CA; ⁷Chariteé Med Sch, Berlin, Germany; ⁸Rochester Univ, Rochester, NY; ⁹UCSF, San Francisco, CA; ¹⁰Auckland Univ, Auckland, New Zealand

Purpose: To develop a consensus-based semi-quantitative tool for MRI-scoring of peripheral psoriatic arthritis (PsA).

Methods: At a 2-day meeting of the OMERACT MRI in Inflammatory Arthritis Special Interest Group in 2007, MRI definitions of key PsA pathologies were agreed by consensus. Furthermore, it was decided which features should be scored. The features (all scored separately at each MCP, PIP and DIP joint) were: Synovitis (range 0-3), flexor tenosynovitis (0-3), periarticular inflammation (0-1, volar and dorsal separately), bone oedema (0-3, proximal and distal bone separately), bone erosion (0-10, proximal and distal bone separately); bone proliferation (0-1). Subsequently, MRI sets of 2nd-5th fingers of 10 PsA patients were read blindly by 8 readers, without formal prior reader calibration. The intraclass correlation coefficients (ICCs, average measure) and smallest detectable difference in percent of average reader max (SDD%max) were calculated.

Results:
MRI definitions (shortened):

Synovitis: Area in the synovial compartment with above-normal post-gd enhancement thicker than the normal synovium.

Tenosynovitis: Signal characteristics consistent with increased water content or abnormal post-gd enhancement adjacent to a tendon, in an area with a tendon sheath.

Periarticular inflammation: Signal characteristics consistent with increased water content or abnormal post-gd enhancement at extraarticular sites (excl. tendon sheaths).

Bone oedema: A lesion within the trabecular bone, with signal characteristics consistent with increased water content and often with ill-defined margins.

Bone erosion: A sharply marginated bone lesion, with typical signal characteristics, which is visible in two planes with a cortical break seen in at least one plane.

Bone proliferation: Abnormal bone formation in the periarticular region.

Interreader agreement: ICC and SDD%max of sum scores were: Synovitis: 0.88 (50%), tenosynovitis 0.84 (74%), periarticular inflammation 0.25 (91%), bone oedema 0.86 (75%), bone erosions 0.91 (65%) and bone proliferation 0.91 (80%). The MRI definitions and the score sheet will be presented at the conference.

Conclusions: MRI definitions of relevant PsA pathologies and a preliminary PsA MRI scoring system were decided by consensus. Using this system, the interreader reliability was good for all parameters except periarticular inflammation. After further development, testing and reader calibration the OMERACT PsAMRIS may prove valuable for use in PsA clinical trials.

Disclosures:

M. Østergaard, None; C. Wiell, None; P. Bird, None; M. Lassere, None; P. Conaghan, None; P. Bøyesen, None; F. Gandjbakhch, None; A. Duer-Jensen, None; C. Peterfy, Synarc Inc, 4; Synarc Inc, 1; Synarc Inc, 3; K. Hermann, None; E. Haavardsholm, None; B. Ejbjerg, None; A. Anandarajah, None; P. Emery, None; H. Genant, None; F. McQueen, None.