Comparison of simultaneous measurements of tympanic membrane temperature and rectal temperature in cats

Rectal temperature (RT) is commonly used in animals to assess core body temperature. However, felines sometimes respond poorly during RT assessment. Therefore, this study compares RT and simultaneous tympanic membrane temperature (TMT) in cats. Eighty-one cats were included in the study. A digital thermometer and a human auricular infrared thermometer were used for RT and TMT measurements. RT measurement was conducted first, followed immediately by TMT measurements of the both ears. The RTs ranged from 35.9°C to 40.5°C, and the TMTs of the right and left ears ranged from 32.2°C to 39.5°C and 34.0°C to 39.5°C, respectively. The TMT of the right ear and RT were significantly correlated (Pearson R2 = 0.694, P <0.001). There was a significant difference between the TMT of the right ear and RT (P < 0.001). The mean difference of the TMT of the right ear was -0.722°C of the RT. The TMTs of both ears were significantly correlated (Pearson R2 = 0.935, P < 0.001). There was no significant difference in the TMTs of the right and left ears (P = 0.131). Forty-five owners (55.56%) felt the cats were more tolerant of TMT than RT measurements. The other thirty-five owners (43.21%) felt there was no difference between the methods. Although the mean TMT was lower than RT, there was a significant correlation between TMT and RT. Veterinarians can use the TMT of either ear to predict the RT. Higher tolerance and shorter measured time may facilitate TMT measurement compared with RT measurement in cats.