A novel fluorescence optical imaging scoring system for hand synovitis in rheumatoid arthritis-validity and agreement with ultrasound

Abstract

Objectives: To develop and validate a new semiquantitative fluorescence optical imaging (FOI) scoring system-the FOI Enhancement-Generated RA Score (FOIE-GRAS) for synovitis assessment in the hand.

Methods: The development of FOIE-GRAS was based on consensus of four experts in musculoskeletal imaging. Forty-six RA patients, eligible for treatment intensification and with ≥1 clinically swollen joints in the hands, and 11 healthy controls were included. FOI, ultrasound and clinical assessment of both hands were obtained at baseline and for RA patients after 3 and 6 months' follow-up. Twenty RA patients had an FOI rescan after 4 h. Synovitis was scored using FOIE-GRAS and the OMERACT ultrasound synovitis scoring system. All FOI images were scored by two readers. Inter-scan, inter- and intra-reader reliability were determined. Furthermore, FOIE-GRAS agreement with ultrasound and responsiveness was assessed.

Results: FOIE-GRAS synovitis was defined as early enhancement, and scores were based on the degree of coverage of the specific joint region after 3 s (0-3). Inter-scan, intra- and inter-reader intraclass correlations coefficients (ICC) were good to excellent for all baseline scores (0.76-0.98) and moderate to good for change (0.65-76).The FOIE-GRAS had moderate agreement with ultrasound (ICC 0.30-0.54) for total score, a good standardized response mean (>0.80), and moderate correlation with clinical joint assessment and DAS28-CRP. The median (interquartile range) reading time per FOI examination was 133 (109, 161) s. Scores were significantly lower in controls [1 (0, 4)] than RA patients [11 (6, 19)].

Conclusion: The FOIE-GRAS offers a feasible and reliable assessment of synovitis in RA, with a moderate correlation with ultrasound and DAS28-CRP, and good responsiveness.

Keywords: FOIE-GRAS; fluorescence optical imaging; imaging; inflammation; outcome measures; rheumatoid arthritis; scoring system; synovitis; ultrasound; validity.