Thermography screening of thyroid gland: how to distinguish health from pathology
This research is organized to investigate if the thermal gradient (T<sub>grad</sub>) (difference between temperature maximum and minimum in the region of interest over thyroid gland on neck thermogramm) could be a marker of normal/ abnormal thyroid function and, if so, find out the cut-off value and check it screening validity. Materials and methods. Thermography examination was performed using a TVS-300 med (S-Petersburg, Russia) thermal imaging camera with a resolution of384 * 288 pixels and sensitivity was <0.04 °C according to European Association of Thermology standards. Anterior neck thermografic images were performed and collected in cloud database, where, by mean of program tools, region of interest were marked and T <sub>grad</sub> calculated. Totally 1025 pts with different tthyroid pathology (group 1: female 944, age 15-90 (55,4±15,8), male 81, age 14-86 (53,6±18,8)), and 395 healthy persons (group 2: male 324 age 17-26 (21,8±4,4), female 71 age 16-70т (34,6±12,7)) were investigated. To check the quality of the model another 314 persons (18 male and 296 female) were studied in screening mode. Results. Calculated Tgrad value was 1,65±0,53<sup>о</sup>С, Ме 1,53(1,24; 1,90) and 0,98±0,23°С, Me 1,01(0,82; 1,15) for group 1 and 2 accordingly. By mean of binary logistic regression analysis we found good correlation between T <sub>grad</sub> value and presence/absence of thyroid pathology: significance level р<0,0001, X<sup>2</sup> =838,84, df=1, β<sub>0</sub> = 9,984, β = -9,033. Area under curve in ROC analysis was 0,922 (95 % CI 0,908; 0,935), р<0,001; optimal cut off value for T<sub>grad</sub> was 1,21<sup>о</sup>С for maximal sensitivity (79,8 %) and specificity (83,3 %). In screening evaluation, according to optimal cut-off value 1,2 °C for Tgrad, 82,2 % of cases were classified correctly: true-positive and true-negative results were achieved in 258 from 314 pts. Conclusion. Thermography test, based on T<sub>grad</sub> value calculation, could help to distinguish persons with normal and abnormal function of thyroid gland..