Quantification of joint blood flow by dynamic contrast-enhanced near-infrared spectroscopy: application to monitoring disease activity in a rat model of rheumatoid arthritis.

Significance: Current guidelines for rheumatoid arthritis (RA) management recommend early treatment with disease modifying antirheumatic drugs (DMARDs). However, DMARD treatment fails in 30% of patients and current monitoring methods can only detect failure after 3 to 6 months of therapy.

Aim: We investigated whether joint blood flow (BF), quantified using dynamic contrast-enhanced time-resolved near-infrared spectroscopy, can monitor disease activity and treatment response in a rat model of RA.

Approach: Ankle joint BF was measured every 5 days in eight rats with adjuvant-induced arthritis (AIA) and four healthy controls. Arthritis was allowed to progress for 20 days before rats with AIA were treated with a DMARD once every 5 days until day 40.

Results: Time and group had separate significant main effects on joint BF; however, there was no significant interaction between time and group despite a notable difference in average joint BF on day 5. Comparison of individual blood flow measures between rats with AIA and control group animals did not reveal a clear response to treatment.

Conclusions: Joint BF time courses could not distinguish between rats with AIA and study controls. Heterogeneous disease response and low temporal frequency of BF measurements may have been important study limitations.