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High Fever, Meet High-Tech Thermometer

Devices: A temporal artery gauge, which detects heat when swept over the forehead, is more precise than many methods.


Remember Mom placing her cool hand on your hot forehead to check for a fever?

Now there's a high-tech version of that loving, motherly gesture: a new type of thermometer that may allow doctors, hospital workers--and moms and dads--to more easily get an accurate temperature reading.

A study published last month in the Archives of Pediatric and Adolescent Medicine found that the temporal artery thermometer detected fevers more often than the popular tympanic thermometer, which is placed in the ear. The method may even prove to be better than taking a rectal temperature, which has been considered the most practical method of getting an accurate reading.

The temporal artery thermometer uses an infrared sensor to detect and measure heat. Roughly the size of a cellular phone, the device is swept over the forehead and detects temperature at numerous points. It then calculates the readings to produce the peak temperature.

The device is gaining support in hospitals and among pediatricians. A Boston company has said it expects to begin marketing a fairly pricey home version of the thermometer later this year.

The new technology "has been carefully thought out, and it's going to be useful," says Dr. Keith Powell, chairman of the department of pediatrics at Northeast Ohio Universities College of Medicine.

Health professionals would welcome a device that would produce an accurate temperature quickly and conveniently. For most people, even those who are mildly sick, knowing that you have a temperature--or the exact degree of the temperature--is not of critical importance. But it's very important for babies and young children, who are less equipped to fight off infection.

"The actual number you get is probably not very important," says Powell. "But it's a clue that something is going on. And as a temperature gets higher, your level of concern goes up."

Doctors also say an accurate reading is crucial among people of any age who have diseases, such as cancer or HIV, that can weaken the immune system.

Taking a temperature is more complicated than most folks would assume. The body's true temperature is best measured in the pulmonary artery--but that requires the insertion of a catheter.

Taking a rectal temperature has long been considered the next-best way to get an accurate reading in a child. For adults and older children, a thermometer placed under the tongue properly (and held for five minutes) is thought to give a fairly accurate result.

Neither method, however, is especially quick or comfortable. And researchers are questioning the accuracy of the rectal method. Their concern is that layers of muscle in the rectum and the presence of stool may prevent that area from heating up as fast as other parts of the body when a fever develops and cooling off when a fever eases.

Thus, researchers have been pursuing a more precise and convenient method.

"There really is a need for something that is quick, accurate, noninvasive and nonirritating," says Dr. Gary Fleisher, a temperature expert at Children's Hospital, Harvard Medical School, and the lead author of the new study.

An alternative way to measure fever emerged in the 1990s with the tympanic thermometer that is inserted in the ear. While the tympanic thermometers have become popular in homes, hospitals and doctors' offices, their accuracy can be less than desired, says Fleisher.

"For those of us in the medical field, it was apparent right away that it wasn't particularly accurate in young children," he says. "If you didn't do it the right way, you can get a false reading."

While trained nurses often get a good reading, he says, parents may not. However, it was "quick and less annoying for the child and much more sanitary [than a rectal thermometer]. So it sort of took off despite the limitations."

Another common method, but one considered highly inaccurate, is the axillary method, in which a thermometer is placed in the armpit. The technique is only about 50% accurate in newborns, says Fleisher.

The recent study suggests that the new temporal artery thermometer might be a better approach. In Fleisher's study, children's fevers were measured with the tympanic and temporal artery thermometers, then compared with rectal temperature readings. The rectal reading were used as the benchmark for accuracy.

The tympanic method detected 49% of all fevers and 76% of high fevers. In contrast, the temporal artery thermometer detected 66% of all fevers and 94% of high fevers.

"If people are currently using an ear thermometer, the temporal artery thermometer is more accurate and easy to use," says Fleisher, who said he has no financial interests in Exergen, the company that is producing the thermometer.

Exergen says it expects the home version of the temporal artery thermometer to sell for about $99.

The method works well, researchers say, because the temporal artery, located in the forehead, is directly connected to the heart through the carotid artery. The temporal artery is also close to the skin's surface.

Nevertheless, there are still questions about how to best obtain an accurate temperature reading, says Powell, because doctors don't really know what "normal" temperatures are in each of the various thermometers. While 98.6 degrees Fahrenheit is the normal average body temperature in healthy people, various thermometers likely give an average temperature reading in healthy people that is somewhat higher or lower than that, he says. Once doctors know what the average normal temperature is using a particular thermometer, it will be possible to identify a true fever using that method.

"I don't think it matters a whole lot how one thermometer compares to another if you know what is normal in that product," Powell says. "The problem is, no one knows what normal is."

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