Is infrared thermometry suitable for the determination of the time since death based on ear temperature? A comparative study of two measurement methods.

Infrared thermometry has been proposed as an interesting alternative to probe thermometers for recording ear temperature in cadavers to estimate the postmortem interval (PMI), but it has still to be validated in this setting. Our objective was to compare the performance of an infrared thermometer to that of a reference probe thermometer for measuring ear temperature. Temperature measurements were performed on 100 cadavers (mean PMI: 4.5 ± 2.5 h) using the infrared and the probe thermometers. The repeatability of the measurements, their correlation, and the agreement between both methods were evaluated. We showed a good repeatability of the measurements with the infrared thermometer (Lin's concordance correlation coefficient (CCC) = 0.93 [0.72;0.98] for the right ear; CCC = 0.94 [0.75;0.98] for the left ear), and there was a strong and significant correlation between measurements provided by the two instruments (p < 0.001). However, a poor agreement was found between both methods, with a systematic underestimation of about 2 °C of the ear temperature when measured with the infrared thermometer. Data from auricular infrared thermometry should not be applied to algorithms developed for probe thermometers to estimate the PMI. Further research is needed to develop a reliable algorithm specifically based on infrared thermometry.