Objective: To perform a retrospective, multicenter observational study that compares the agreement of rectal temperature with the temperature measured with noncontact infrared thermometer (NCIT) in a population of dogs and cats.
Animals: 168 dogs and 61 cats.
Procedures: NCIT readings were taken in triplicate from the medial pinna, then rectal temperature was taken with a standard digital rectal thermometer (RT). Ambient room temperature, signalment, presence of icterus, skin and coat color, reason for presentation, and final diagnosis were recorded.
Results: In dogs, median (range) body temperature reflected by RT and NCIT measurements was 38.4 °C (33.4 to 40.3 °C) and 36.3 °C (30.8 to 40.0 °C), respectively. In cats, median (range) body temperature reflected by RT and NCIT measurements was 38.3 °C (36.2 to 40.0 °C) and 35.7 °C (31.8 to 38.0 °C), respectively. There was a weak positive correlation between body temperatures measured by NCIT and RT in dogs (Kendall tau = 0.154), but there was no correlation in cats (Kendall tau = -0.01). A significant, albeit weak, agreement was seen between temperature measured by NCIT and RT in dogs (Kappa value, 0.05), but not cats (Kappa value, -0.08). In both species, NCIT tended to underread body temperature, compared with RT (dogs: mean ± SD bias -2.2 ± 1.51 °C; cats: mean bias -2.7 ± 1.44 °C), with the degree of low measurements lessening as body temperature increased.
Clinical relevance: Given both poor correlation and agreement in body temperature measured by NCIT and rectal thermometer, NCIT measurements cannot be recommended at the current time as a means to determine body temperature in dogs and cats.