Comparison of rectal and tympanic thermometry in chinchillas (Chinchilla lanigera)

OBJECTIVE To evaluate the effects of restraint time and thermometer insertion depth on rectal temperature measurements in chinchillas and determine the extent of agreement between temperatures measured with 2 tympanic and a rectal thermometer. DESIGN Prospective method comparison study. ANIMALS 47 healthy chinchillas. PROCEDURES Effects of 1- and 2-cm rectal thermometer insertion depths and the effect of manual restraint for up to 5 minutes were evaluated. Near simultaneous temperature measurements were obtained with a human tympanic, a veterinary tympanic, and a rectal thermometer by 2 observers. Duplicate temperature measurements were obtained for each method, and the sequence of measurements was randomized for each animal. RESULTS Rectal temperature readings obtained at a depth of 2 cm were significantly higher (mean ± SD, 1.14 ± 0.77°C [2.05° ± 1.39°F]) than those obtained at 1 cm. After 3 minutes, manual restraint had a significant effect on rectal temperature. The reference interval for rectal temperature in chinchillas with a 2-cm thermometer insertion depth was calculated as 34.9° to 37.9°C (94.8° to 100.2°F). Both tympanic infrared thermometers had significant systematic bias (0.42 ± 0.12°C [0.76° ± 0.22°F]) and proportional bias (0.88 ± 0.14°C [1.58° ± 0.25°F]). The coefficients of reliability for the rectal thermometer, the human tympanic thermometer, and the veterinary tympanic thermometer were 0.86, 0.85, and 0.69, respectively. CONCLUSIONS AND CLINICAL RELEVANCE Rectal thermometer insertion depth and duration of manual restraint had a significant effect on rectal temperature measurements in chinchillas. Because of significant systematic and proportional bias, tympanic thermometry was not considered a suitable replacement for rectal thermometry in chinchillas.