Role of Infrared Imaging for Detection of Subclinical Inflammation of Joints: A Prospective Cohort Study

Introduction: The detection of inflammation is important for diagnosis of inflammatory joint diseases and its severity. There are clinically doubtful cases of inflammation of joints. Advanced thermal cameras are able to detect the presence of inflammation. Hence, thermal imaging technology has been used for detection of this type of subclinical inflammation of joints.

Aim: To study the efficacy of infrared imaging to detect the subclinical inflammation of joints in doubtful cases of arthritis.

Materials and Methods: A prospective cohort study was conducted for a period of one year from January 2016 to June 2017. The study comprised of 60 patients of all age groups. Patients with joint pain attending Outpatient Department (OPD) of Physical Medicine and Rehabilitation Department (PMR), Agartala Government Medical College (AGMC) and Govind Ballav Pant Hospital (GBPH), Agartala, India, irrespective of the duration of illness and diseases were selected considering inclusion and exclusion criteria. They were evaluated clinically (swelling, tenderness, redness, increased temperature and the presence of restriction of movement) for presence of inflammation in the joint. Blood tests were done for Acute Phase Reactant (APR) namely Erythrocyte Sedimentation Rate (ESR) and C-Reactive Protein (CRP) and infrared imaging of the respective joints were taken. On the basis of clinical examination, all these patients were divided in three groups: (i) patients with inflamed joint; (ii) non inflamed joint; and (iii) doubtful inflammation of joints. Infrared imaging of all the respective joints of all the patients were compared with the respective results of APR for presence of inflammation. Values more than the normal range of APR were considered as positive marker for inflammation. The data was analysed statistically by calculating sensitivity, specificity, Positive Predictive Value (PPV) and Negative Predictive Value (NPV) using Matrix Laboratory (MATLAB) 2013b software.

Results: Out of 60 cases, 37 (61.66%) patients showed clinically inflamed joints, 10 (16.66%) showed no inflammation and 13 (21.66%) showed clinically doubtful cases of inflammation. The results were statistically analysed and the sensitivity, specificity, PPV and NPV of infrared imaging for detection of joint inflammation were 91%, 80%, 94% and 72%, respectively.

Conclusion: Infrared imaging is a very sensitive tool for the detection of inflammation of joints and is very useful for detection of subclinical inflammation of joint.