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Purpose:
The aim of this study was to test cross-sectional and longitudinal inter- and intra reader reliability of the Psoriatic Arthritis Magnetic Resonance Imaging Score (PsAMRIS) under standardized conditions.
Methods:
The exercise was performed using MRI scans from 12 PsA patients (8 acquired in Copenhagen and 4 in Leeds) before and after 12 months of anti-TNFα therapy. The metacarpophalangeal (MCP), proximal interphalangeal (PIP), and distal interphalangeal (DIP) joints of the 2nd–5th fingers were examined, using a 0.6 T MRI unit (Copenhagen) and a 0.2T MRI unit (Leeds). Coronal, axial and sagittal T1-weighted pre- and post-gadolinium-contrast images and sagittal and axial pre-contrast STIR images were obtained, anonymized and blinded for time sequence and read twice by FG, FMQ, MØ and PB on identical PACS workstations. For the second reading the images were re-anonymized and re-randomised. The images were scored according to the PsAMRIS: at MCP, PIP and DIP joint-level synovitis was scored 0-3, tenosynovitis 0-3, bone proliferation 0-2, pariarticular inflammation 0-2, bone marrow edema 0-3 per bone and bone erosions 0-10 per bone. Inter-reader reliability was assessed using average measure intraclass correlations coefficient (ICCa) and intra-reader reliability by single measures intraclass correlations coefficient (ICCs).
Results:
The median (IQR) average baseline/1-year follow-up synovitis score was 10.8 (8.5-14.3)/ 8.4 (6.7-9.7), tenosynovitis score 5.7 (1.7-8.5)/ 2.0 (0.9-4.4), bone proliferation 2.2 (1.4-3.9)/ 2.2 (1.4-3.9), periarticular inflammation 1.1 (0.1-3.6)/ 0.5 (0.3-0.6), bone marrow edema 0.3 (0.1-1.4)/ 0.1 (0.0-0.8) and bone erosions 1.8 (0.2-5.1)/ 1.9 (0.1-5.0). The cross-sectional inter-and intra reader reliability as well as the inter-reader reliability for 1-year change are presented in table 1. The inter-reader ICC was high for all measures except moderate for bone proliferation. Poor ICCs for bone proliferation and erosion change scores are explained by minimal change in the 1-year period.
Conclusion:
In this multi-reader exercise testing the PsAMRIS under standardized conditions, very high interreader and intrareader reliability for status and change scores for most parameters and readers were found. Inflammatory parameters performed best. These results suggest that PsAMRIS is a reliable tool for MRI assessment of PsA patients.
Table 1. Cross sectional inter- and intra reader reliability | ||||||
Inter-reader reliability (ICCa) | Intra-reader reliability (ICCs) (cross-sectional) | |||||
Cross-sectional | 1-year change | Reader 1 | Reader 2 | Reader 3 | Reader 4 | |
PsA synovitis | 0.95 | 0.95 | 0.97 | 0.73 | 0.93 | 0.90 |
PsA flexor tenosynovitis | 0.97 | 0.95 | 0.81 | 0.74 | 0.93 | 0.73 |
PsA bone proliferation | 0.77 | 0.10 | 0.20 | 0.84 | 0.79 | 0.44 |
PsA periarticular inflammation | 0.91 | 0.91 | 0.39 | 0.95 | 0.88 | 0.91 |
PsA bone marrow edema | 0.87 | 0.87 | 0.98 | 0.97 | 0.99 | 0.03 |
PsA bone erosion | 0.97 | 0.44 | 0.91 | 0.93 | 0.92 | 0.91 |