Medical thermography: a diagnostic approach for type 2 diabetes based on non-contact infrared thermal imaging

To test the potential of Infrared (IR) thermography in diagnosing as well as predicting type 2 diabetes and its complications compared with biochemical assay of HbA_1c as standard. As per American Diabetes Association criteria, threshold for diagnosis of diabetes was set as HbA_1c ≥ 6.5 % (7.7 mmol L⁻¹). The total subjects (n = 62) were studied out of which control (n = 32) and diabetic subjects (n = 30). IR camera was used to capture the thermal images of the skin for diagnosis of the disease; receiver operating characteristic (ROC) curve was used to set temperature (°C) as threshold for statistically significant body regions under t test. In diabetic group, HbA_1c showed negative correlation with carotid region (r = −0.471, p < 0.01) and the mean skin temperature was lower than the normal group at body regions namely knee (p = 0.002), tibia (p = 0.003), forehead (p = 0.014), and palm (p = 0.019). The palm region showed highest area under the curve of 0.711 (95 % CI: 0.581–0.842) and the threshold was set as ≤33.85 °C, thereby sensitivity (90 %) and specificity (56 %) was obtained in determining the undiagnosed diabetes with positive predictive value of 65 %, negative predictive value of 85 % and accuracy of 73 %. As HbA_1c increases, skin temperature decreases. Skin temperature enables early detection of diabetes as compared to HbA_1c. The decrease in skin temperature may be due to the decrease in the basal metabolic rate, poor blood perfusion and high insulin resistance. Thermography can be used as a diagnostic as well as prognostic tool for the diabetes.