Comparison of temperature readings from a percutaneous thermal sensing microchip with temperature readings from a digital rectal thermometer in equids

Objective - To compare temperature readings from an implantable percutaneous thermal sensing microchip with temperature readings from a digital rectal thermometer, to identify factors that affect microchip readings, and to estimate the sensitivity and specificity of the microchip for fever detection. Design - Prospective study. Animals - 52 Welsh pony foals that were 6 to 10 months old and 30 Quarter Horses that were 2 years old. Procedures - Data were collected in summer, winter, and fall in groups 1 (n = 23 ponies), 2 (29 ponies), and 3 (30 Quarter Horses), respectively. Temperature readings from a digital rectal thermometer and a percutaneous thermal sensing microchip as well as ambient temperature were recorded daily for 17, 23, and 19 days in groups 1 through 3, respectively. Effects of ambient temperature and rectal temperature on thermal sensor readings were estimated. Sensitivity and specificity of the thermal sensor for detection of fever (rectal temperature, ≥ 38.9°C [102°F]) were estimated separately for data collection at ambient temperatures ≤ 15.6°C (60°F) and > 15.6°C. Results - Mean ambient temperatures were 29.0°C (84.2°F), -2.7°C (27.1°F), and 10.4°C (50.8°F) for groups 1 through 3, respectively. Thermal sensor readings varied with ambient temperature and rectal temperature. Rectal temperatures ranged from 36.2° to 41.7°C (97.2° to 107°F), whereas thermal sensor temperature readings ranged from 23.9° (75°F) to 42.2°C (75° to 108°F). Sensitivity for fever detection was 87.4%, 53.3%, and 58.3% in groups 1 to 3, respectively. Conclusions and Clinical Relevance - The thermal sensor appeared to have potential use for initial screening of body temperature in equids at ambient temperatures > 15.6°C.