Are Ear Thermometers Accurate?

Aug. 22, 2002 -- Those infrared ear thermometers that have become so popular with pediatricians and parents are fast and easy to use, but are they accurate? A review of the research suggests they may not be, and while temperature variations are slight, they could make a difference in how a child is treated.

Researchers found temperature discrepancies of as much as 1 degree in either direction when ear thermometer readings were compared with rectal thermometer readings, the most accurate form of measurement. They concluded that ear thermometers are not accurate enough to be used in situations where body temperature needs to be measured with precision.

"In most clinical settings, the difference probably doesn't represent a problem," author Rosalind L. Smyth, MD, tells WebMD. "But there are situations where 1 degree could determine whether a child will be treated or not."

Smyth and colleagues from England's University of Liverpool reviewed 31 studies comparing ear and rectal thermometer readings in some 4,500 infants and children. Their findings are reported in the Aug. 24 issue of The Lancet.

The researchers found that a temperature of 100.4(F (38(C) measured rectally could range anywhere from 98.6(F (37(C) to 102.6(F (39.2(C) when using an ear thermometer. Smyth says the results do not mean that infrared ear thermometers should be abandoned by pediatricians and parents, but rather that a single ear reading should not be used to determine the course of treatment.

Pediatrician Robert Walker does not use ear thermometers in his practice and does not recommend them for his patients. He expressed surprise that the discrepancy between ear and rectal readings was not greater in the review.

"In my clinical experience the ear thermometer often gives a false reading, especially if a child has a very bad ear infection," Walker tells WebMD. "A lot of parents are uncomfortable taking rectal temperatures, but I still feel that they are the best way to get an accurate reading."

The American Academy of Pediatrics (AAP) recently advised parents to stop using glass mercury thermometers because of concerns about mercury exposure. Walker says the newer digital thermometers give a very accurate reading when inserted rectally. Walker serves on the AAP's Committee on Practice and Ambulatory Medicine and practices in Columbia, S.C.

"No matter which method you choose, my main message to parents is that it is more important to look at the child than the thermometer reading," he says. "You can have a very ill child with a fairly normal temperature. And a child might have a temperature of 102 degrees, but if he is running around and playing and drinking well, chances are he doesn't have anything too severe."