Is a tympanic (ear) temperature higher than an oral temperature?

From the Guidelines

Tympanic temperature is not consistently higher than oral temperature, and its accuracy can be affected by various factors. When comparing the two, studies have shown that oral temperature measurements are generally more reliable and accurate in reflecting core body temperature 1. The main differences between tympanic and oral temperatures are due to the distinct methods of measurement: tympanic thermometers detect infrared heat emitted from the tympanic membrane, while oral thermometers measure the temperature under the tongue. Some key points to consider include:

• Tympanic membrane temperature reflects the temperature of the hypothalamus (core), but its measurement can be influenced by factors such as inflammation or blockage of the auditory canal, and operator error 1.
• Oral temperature measurements can be distorted by mouth breathing, hot or cold fluids, or gases in or near the mouth, but are generally more accurate and reliable for clinical decision-making 1.
• The accuracy of tympanic thermometers can be affected by ear canal anatomy, cerumen (earwax), and improper positioning of the thermometer, making oral temperature a more consistent and reliable choice for tracking temperature changes over time 1. In clinical practice, it is essential to consider these factors and choose the most appropriate method for temperature measurement, taking into account the patient's condition, cooperation, and the potential for environmental influences on the measurement.

From the Research

Comparison of Tympanic and Oral Temperatures

• The study by 2 found that there was no significant difference between average tympanic and average oral temperatures, suggesting that tympanic temperatures may be comparable to oral temperatures.
• However, the study by 3 found that oral thermometers registered higher temperatures in 69% of subjects, and that tympanic thermometers gave presumably higher temperature readings than oral thermometers.
• The study by 4 found that the mean temperature for tympanic membrane (TM) temperatures was 99.6°F, which was higher than the mean oral temperature of 98.3°F, but the difference between TM and rectal temperatures was only 0.22°F.
• The study by 5 found that the temperature difference between mean ear and oral measurements was -0.20 degrees +/- 0.59 degrees C, suggesting that tympanic temperatures may be slightly lower than oral temperatures.

Accuracy of Tympanic and Oral Temperatures

• The study by 6 found that electronic rectal temperature measurements were the most accurate, and that electronic tympanic, oral, and axillary measurements gave unacceptable standard deviations of temperature differences.
• The study by 4 found that oral and tympanic temperature readings are not equivalent to rectal thermometry readings, and that oral thermometry frequently underestimates the temperature relative to rectal readings, while TM values can either under- or overestimate the rectal temperature.
• The study by 5 found that there was a strong correspondence between ear temperatures and oral and rectal temperatures, but that parents were not as confident of ear temperatures' accuracy.