Background/Purpose:

Dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) has been validated in rheumatoid arthritis for measuring inflammation, but has rarely been studied in psoriatic arthritis (PsA).

The purpose was to investigate whether DCE-MRI can discriminate PsA patients with high disease activity from minimal disease activity (MDA)(1), and to correlate DCE-MRI findings with conventional MRI and clinical measures.

Methods:

PsA patients fulfilling CASPAR criteria were eligible in this investigator-initiated study of patients with either high disease activity (group 1) or MDA (group 2). Inclusion criteria were for group 1: swollen joint count (SJC)≥6, tender joints count (TJC)≥6, hand involvement and clinical indication for initiation of anti-TNF therapy, and for group 2: hand involvement within 1 year, long-term treatment with adalimumab 40 mg eow, and fulfilling criteria for MDA (at least 5 out of 7: TJC≤1; SJC≤1; body surface area≤3%; PtGA≤20; pain≤15; HAQ≤0.5; 13-enthesitis≤1). DAS28 and the new Disease Activity index for PSoriatic Arthritis (DAPSA)(2) score (sum of SCJ, TJC, PtGA, pain and CRP) was calculated. The validated PsAMRIS scoring system (3) was used for analyzing conventional MRI (0.6 tesla). PsAMRIS total inflammation was calculated by adding synovitis, flexor tenosynovitis, periarticular inflammation and bone marrow oedema scores. DCE-MRI were analysed by Dynamika software (Image Analysis Ltd., Leeds, UK). Regions of interest (ROIs) were drawn around 2.-5. metacarpophalalangeal joints, excluding large blood vessels. The ROIs were used for automatic computing of the number of pixels with plateau and washout pattern (N_p+w), the initial rate of enhancement (IRE), and maximum enhancement (ME).

Results:

Patient characteristics were: 9 males/8 females, median age 45 (25-63) years, joint/skin disease duration 8 (2-59)/15(2-59) years (no difference between groups). Clinical and imaging data are shown in the table. 

	Group 1: High disease activity (n=9)	Group 2: Minimal Disease Activity (n=8)	P value
Np+w	712 (13-1587)	362 (25-1316)	0.25
IRE x 103	8 (5-33)	10 (6-14)	0.29
ME	1.20(1.17-1.33)	1.21 (1.16-1.33)	0.92
Np+w* IRE	5.4(0.4-15.9)	2.8 (0.2-13.2)	0.44
Np+w* ME	946(16-1903)	434 (29-1608)	0.29
PsAMRIS synovitis	3 (0-5)	2 (0-5)	0.59
PsAMRIS total inflammation	16 (1-24)	7.5 (3-18)	0.19
DAS28 score	5.5 (3.9-6.4)	1.4 (1.1-2.4)	0.01
DAPSA score	64.9 (30.9-103.3)	2.4 (0.1-5.6)	0.01

Median (range). Groups compared using Krustal-Wallis test.

We found a significant correlation between the DCE-MRI parameters (N_p+w*IRE, N_p+w*ME  and N_p+w) and PsAMRIS total inflammation (Spearman’s rho: 0.53, 0.51 and 0.51; all P<0.05).  DCE-MRI parameters were not statistically significant correlated with clinical measures, but N_p+w*IRE, N_p+w*ME  and N_p+wwere numerically lower in the MDA group.

Conclusion:

DCE-MRI parameters correlated significantly with PsAMRIS total inflammation score, and showed a trend toward higher values in the high disease activity versus the MDA group. DCE-MRI is a promising method for assessing joint inflammation in PsA. However, a larger longitudinal study is needed to clarify, if DCE-MRI is superior to conventional MRI for discriminating between disease activity levels.

Ref: 1. Coates, ARD 2009; 2. FitzGerald, ARD 2011; 3. Østergaard, JRheum 2009

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