Refinement of the Collagen Induced Arthritis Model in Rats by Infrared Thermography

Aims: Collagen induced arthritis in rats is an important model for human rheumatoid arthritis. This study was designed to improve and refine this model by use of infrared thermography by measuring surface temperature of hind feet. Our hypothesis is that the local temperature on the feet correlates with other clinical parameters such as clinical score and edema and may serve as a method for quantification of the degree of inflammation.
Study design: Experimental animal study.
Place and Duration of Study: Institute of Biomedicine, University of Aarhus, Denmark between February and March 2010.
Methodology: Arthritis was induced with collagen immunization in sixteen Lewis rats. Four of the animals were treated with dexamethasone to function as negative controls. Clinical scores were based on the magnitude of paw edema. The mean temperature of the hind feet (region covering the metatarsus and tarsus) was normalized with a reference area on the back of the same rat. The temperature index were compared with the clinical score index, edema index, and bodyweight of the rats
Results: The mean hind feet temperatures increased with increasing clinical severity in the acute stage of the disease. There were positive correlation between temperature and clinical scores.

Conclusion: The thermographic response appeared prior to the clinical signs, suggesting that thermography may be used as a predictive sign for the development of disease. This technique could be a non-invasive, objective, rapid, and reproducible method for evaluation of the degree of inflammation and effect of therapeutic interventions.