Measurement of Body Temperature in 300 Dogs with a Novel Noncontact Infrared Thermometer on the Cornea in Comparison to a Standard Rectal Digital Thermometer

Objective: To assess the accuracy of obtaining body temperatures in dogs with a noncontact infrared thermometer (NCIT) on the cornea compared with a rectal digital thermometer (RDT).

Design: Prospective single center study.

Setting: University teaching hospital.

Animals: Three hundred dogs presented with low, normal, or high body temperatures.

Interventions: Three body temperature readings were measured by an RDT and by an NCIT on the cornea of the left eye by 2 investigators (experienced and inexperienced). Results obtained by the 2 methods were compared.

Measurements And Main Results: Median body temperature measured by the experienced investigator with the RDT and the NCIT were 38.3°C (range 35.5°C-41.1°C; 95% CI: 38.2-38.4°C) and 37.7°C (35.9°C-40.1°C; 95% CI: 37.7°C-37.9°C), respectively. Measurement of RDT as well as of NCIT correlated well between both investigators (rRDT = 0.94; rNCIT = 0.82; respectively, P < 0.001 for both methods). Mean RDT and NCIT-temperature correlated poorly (r = 0.43; P < 0.001) when taken by the experienced investigator and even less by the nonexperienced investigator (r = 0.38; P < 0.001). Repeatability of the NCIT revealed an unsatisfactory value (0.24°C) compared to RDT measurement (0.12°C). Agreement between both devices in measuring low, normal, and high values, calculated by Cohens-Kappa, was unsatisfactory (к = 0.201; P < 0.001). Calculating the receiver operating characteristic curve to determine the best threshold for fever (defined as RDT temperature >39.0°C) showed an area under the curve of 0.76. Mean discomfort score was significantly lower using NCIT compared to RDT measurement (P < 0.001).

Conclusions: There was poor agreement between body temperatures obtained by RDT and NCIT. The corneal NCIT measurement tends to underrecognize hypothermic and hyperthermic conditions. Although the use of the NCIT yields faster results and is significantly more comfortable for the dog than the RDT measurement, it cannot be recommended in dogs at this time.