NEW YORK, Jul 27 (Reuters) -- Some infrared ear thermometers may give inaccurate readings of body temperature, according to a study in the July issue of the Southern Medical Journal.
But the manufacturer of one of the thermometers used in the study counters the conclusion, saying that the researchers may not have used the instrument correctly, which affects its accuracy.
The thermometers, known as infrared tympanic thermometers, are widely used in homes, clinics, and hospitals. The devices are inserted into the ear canal, where they compute internal body temperature by measuring infrared radiation from the eardrum, or tympanic membrane. Several studies have concluded that "tympanic membrane temperature more accurately reflects and tracks core body temperature than does oral temperature," note the study authors.
But other studies have suggested that some commonly used infrared ear thermometers may give inaccurate readings, according to a team of researchers led by Dr. Jack G. Modell, of the University of Alabama at Birmingham School of Medicine.
In a handful of cases, Modell and colleagues found that "falsely elevated temperature readings led to unnecessary and costly testing to determine the cause of the apparent fevers," the researchers write. In others, "falsely low temperature readings by an infrared tympanic thermometer led to a delay in diagnosis and treatment," they report.
To check the accuracy of such thermometers, the researchers used two -- the Diatek 9000 Infrared Aural Thermometer and the IVAC 2090 Core Check Tympanic Thermometer -- to measure the temperatures of 137 adult volunteers.
The researchers measured the temperature in the left and right ear of each volunteer. They compared readings from the two models to each other, as well as to two different oral thermometers -- an electronic one and a conventional glass mercury thermometer.
The two tympanic thermometers often registered different temperatures in the same volunteer, the researchers found. And readings from one of the two models, the IVAC, tended to be lower than readings from the electronic oral and glass mercury thermometers, they report.
"Temperature differences considered large enough to be of potential clinical significance (greater than 0.5 degrees Celsius) occurred almost one fourth of the time between ears with both the IVAC and Diatek thermometers, one third to one half of the time between the tympanic and oral thermometers, and nearly two thirds of the time between the two brands of tympanic thermometer," they write.
"Although it is possible that tympanic thermometer brands, models, or particular units by the same manufacturer are more accurate than those we used, the unpredictable variability and inaccuracy of temperatures measured by the infrared tympanic thermometers in this and previous studies are sufficiently large to render the use of these devices for clinical thermometry potentially dangerous," the researchers conclude.
They advise that if an infrared tympanic thermometers is used, "that the thermometer first be subjected to comparative testing... to be certain that it is sufficiently reliable...."
In a written response to the study, the manufacturer of the IVAC thermometer, ALARIS Medical Systems of San Diego, California, told Reuters Health that other independent research has concluded its thermometer is extremely accurate.
"Infrared thermometry is an established and accepted method for measuring a patient's core temperature," according to the company statement. "It is well documented in the literature that proper positioning technique is essential," it adds, suggesting that the authors of the study may not have used the thermometers properly.
The manufacturer of the Diatek thermometer did not respond to a request for comment on the study.
SOURCE: Southern Medical Journal 1998;91:649-655.
