Patients
Twenty-one patients with PsA (mean age of 47±6 years, minimum/maximum 26/72 years, male/female 11/10), fulfilling the CASPAR criteria, with a mean disease duration 4±3.6 years and suffering from peripheral joint involvement of at least two metacarpophalangeal (MCP) joints and dactylitis of at least one finger were prospectively recruited for the “Analysis of the DActylic Melange” (ADAM) research initiative. All patients had failed methotrexate (MTX) monotherapy and were escalated to Etanercept (Enbrel® 50 mg s.c.) fortnightly after a baseline MRI scan. Seventeen patients (mean age of 53.7±11.6 years, minimum/maximum 26/72 years, male/female 9/8) were included. Follow-up was available in 13 patients (mean age of 57±9.01 years, minimum/maximum 42/73, male/female 7/6) at 6.2±0.85 months (minimum/maximum, 5/8 months) after treatment escalation. The study was approved by the local ethics committee. Written and informed consent was obtained from all patients before the initiation of the study. The Disease Activity Score 28 (DAS 28) was 2.42±0.72 (minimum 1.8/maximum 4.3, median 2.2) at baseline and 2.06±0.27 (minimum 1.6/maximum 2.5, median 2.1). C-reactive protein (CRP) levels were 0.87±1.35 mg/dL (minimum 0.1/maximum 5.8, median 0.3) at baseline and 0.43±0.27 mg/dL (minimum 0.1/maximum 1.1, median 0.4) at follow-up.
MRI
Baseline (T0) and follow-up (T1) MR imaging of the clinically dominant hand were performed using a 3T MRI scanner (Magnetom Skyra, Siemens Healthineers) and a dedicated 16-channel hand coil (3T Tim Coil, Siemens Healthineers). The imaging protocol follows the recommendations of the OMERACT working group and includes pre- and post-contrast (gadolinium-based, intravenous-injection of 0.4 mL/kg bodyweight) T1-weighted and non-contrast fat-saturated T2-weighted/ short tau inversion recovery (STIR) images in two different orthogonal planes.
In detail, the following sequences were used:
Coronal T1 turbo spin echo (TSE) (TR/TE in ms, 862/27, flip angle in °, 150, slice thickness in mm, 2.5, field of view in mm, 140), coronal STIR (TR/TE in ms, 5560/31, flip angle in °, 120, slice thickness in mm, 2.5, field of view in mm, 140), sagittal proton density (PD) TSE fat-saturated (TR/TE in ms 3150/47, flip angle 150°, slice thickness 2.5 mm, field of view 150 mm), transversal T2 TSE fat-saturated (TR/TE in ms: 5693.8/89, flip angle 180°, slice thickness 3.0 mm, field of view: 160 mm), transversal T1 SE fat-saturated after iv contrast (TR/TE in ms, 807/16, flip angle in °, 90, slice thickness in mm, 3.0, field of view in mm, PsA:130), and coronal T1 TSE after iv contrast (TR/TE in ms, 862/27, flip angle in °, 150, slice thickness in mm, 2.5, field of view in mm, PsA; 140).
Image analysis
MR images were read and analyzed in consensus by two radiologists and one rheumatologist trained in PsAMRIS-Scoring, according to the OMERACT PsAMRIS guidelines [15,16]. In the case of different scores, the analysts decided scorings by common agreement. Images were evaluated for synovitis (score 0–3), flexor tenosynovitis (score 0–3), periarticular inflammation (score 0 or 1), bone edema (score 0–3), bone erosion (score 0–10), and bone proliferation (score 0 or 1) for the MCP (metacarpophalangeal), PIP (proximal interphalangeal), and DIP (distal interphalangeal) joint region of fingers 2–5, according to the OMERACT PsAMRIS guidelines [15]. In all joints, the proximal and distal or the dorsal and palmar portions, respectively, were analyzed separately for the presence of bone edema and erosions or periarticular inflammation. For comparison of time effort, one highly trained radiologist (CS) timed the scoring of PsAMRIS and sPsAMRIS.
Development of a simplified psoriatic arthritis MRI score, sPsAMRIS
For the development of a simplified scoring system, sPsAMRIS, we applied a single-site weighted summation approach. Priority was assigned to the joints with the highest standardized response mean (SRM) for the change of overall PsAMRIS at baseline and at follow up (Table 3)
All statistical analyses were performed using the R project for statistical computing (version 3.5.1 “feather spray”, the R foundation). For descriptive analysis mean, standard deviation, minimum, and maximum were presented. The sensitivity for change and their responsiveness was calculated by SRM for PsAMRIS and sPsAMRIS, as follows: SRM= . Relative efficiency (RE) was calculated for sPsAMRIS compared to PsAMRIS as a reference, as follows: RM= 2. Confidence bounds for the RE were estimated by the bootstrap method (based on B=5000 bootstraps with replacement) and application of the percentile method. A RE>1 indicates that sPsAMRIS is more efficient than PsAMRIS in detecting change. For correlation analyses, Pearson’s product-moment correlation with Pearson’s correlation coefficient, r, was used. A p-value of <0.05 was considered to be significant. Inter- and intra-rater reliability was calculated by two-way mixed intraclass correlation coefficients [single-measure ICC (sICC) for intra-rater and average-measure ICC (aICC) for inter-rater reliability].