Background Altered microcirculation (abnormal perfusion/capillary leakage) of synovial tissue can be detected early using Fluorescence Optical Imaging (FOI). FOI utilizes an intravenous fluorophore1,2 that displays high-resolution hand images that can be analyzed visually (FOI-v) in real-time, or by using digital Disease ACTivity (DACT) scoring methods. We previously reported FOI's sensitivity and specificity in detecting silent synovitis in various rheumatic diseases1.
Objectives Here, we test the diagnostic performance of FOI-DACT in detecting subtle hand joint inflammation in early rheumatoid arthritis (eRA), as compared to clinical evaluation and MusculoSkeletal UltraSound (MSUS).
Methods Fingers and wrists of patients with eRA were assessed by clinical examination, MSUS and FOI-DACT imaging. Inflammation was defined as having synovial hypertrophy/effusions and intra-articular Doppler signaling on MSUS, and as increased optical intensities on FOI-v. Scores of DACT≥1 were considered indicative of disease activity.
Results 1326 joints of 39 eRA patients [72% females, 56% previous/current smokers, 54% RF(+) and 69% ACPA(+)] were studied. The incidence and mean number ±SD of joints inflamed by clinical, MSUS and FOI-v were 23% (7.8±8.1), 29% (9.7±7.7) and 30% (10.3±7.2), respectively. Using MSUS as a reference, FOI-DACT was 95% (35/37) accurate in identifying patients with active disease, 24% (9/37) of whom had erosive RA. High correlations and agreements emerged between MSUS and FOI-v (r=0.803, p<0.001; kappa±SE:0.70±0.02 [95% CI 0.67–0.75]), clinical and FOI-v (r=0.732, p<0.001; kappa±SE:0.56±0.03 [95% CI 0.51–0.61]) and MSUS and clinical (r=0.793, p<0.001; kappa±SE:0.59±0.03 [95% CI 0.54–0.64]). The sensitivity, specificity, NPV and PPV of inflammation by FOI-v was 81% (308/380), 90% (854/946), 61%, and 96% respectively. Of the clinically negative but MSUS positive (145/1023) joints, 68% (Subclinical: 98/145) were also FOI positive. Remarkably, one patient had 15 joints that were FOI-DACT positive and MSUS negative, but a month later, the same joints became MSUS positive. Although the wrists and MCPs were frequently inflamed, DIP joint inflammation was noted in 12 patients by FOI-DACT and MSUS. Nine of these patients had osteoarthritis by conventional radiography.
Conclusions In early RA, Fluorescence Optical Imaging (FOI) coupled with digital Disease ACTivity (DACT) scoring correlates well with MSUS, and has a high positive predictive value. FOI-DACT emerges as a useful automated quantitative scoring method for synovial inflammation, and may be used in monitoring the effects of therapy.
Kisten Y, Györi N, af Klint E, et al. 2015 Detection of clinically manifest and silent synovitis in the hands and wrists by fluorescence optical imaging. RMD Open 2015;1: e000106. doi: 10.1136/rmdopen-2015-000106 (http://rmdopen.bmj.com/content/1/1/e000106.full.pdf+html)
Glimm AM, Werner SG, et al. Analysis of distribution and severity of inflammation in patients with osteoarthitis compared to rheumatoid arthritis by ICG-enhanced fluorescence optical imaging and musculoskeletal ultrasound: a pilot study. Annals of the Rheumatic Diseases. Published online Aug. 26, 2015. (http://dx.doi.org/10.1136/annrheumdis-2015-207345).
Disclosure of Interest None declared