Taking a child’s temperature orally or rectally can be challenging, because children are often restless or uncooperative, especially when they’re feeling sick. For this reason, nearly two thirds of pediatricians (and many parents) use infrared ear thermometers to measure body temperature in children. The ear is more accessible than the rectum and safer than the mouth, and infrared ear thermometers measure temperature more quickly than mercury or electronic thermometers. But do they measure core body temperature as accurately as rectal thermometers? Research in the August 24, 2002 issue of
suggests that infrared ear thermometers do not measure core body temperature as accurately as rectal thermometers.
This study was a meta-analysis, which means that researchers reviewed numerous studies in an attempt to derive an overall estimate of how well temperatures taken with infrared ear thermometers correlate to temperatures taken with rectal thermometers. Researchers from the University of Liverpool in England reviewed 31 studies comparing rectal temperature and ear temperature taken from the same child. Only studies conducted in children (under 18 years of age) were included in this analysis. Children with hypothermia (low body temperature) and preterm infants were excluded from the study.
Rectal temperature was chosen as the standard for comparison because rectal temperature has been shown to accurately predict core body temperature measured in the pulmonary artery—a method only used in critically ill patients.
The researchers analyzed the difference between temperatures taken at the ear with an infrared thermometer and temperatures taken at the rectum with either a mercury, electronic, or internal probe thermometer.
When all 31 studies were considered together, the average difference in temperature between ear and rectal temperature was 0.29 degrees Celsius. Statistical tests indicated that this small difference was not significant.
However, the range of differing temperatures between rectal and ear measurement was rather broad. For example, a temperature measured at the rectum as 38 degrees Celsius in a given child, might be measured as anywhere from 37.04 degrees to 39.20 degrees at the child’s ear. Differences of one or two degrees centigrade can affect parents’ decisions about whether or not to call the doctor and doctors’ decisions about how to treat an ill child.
Although these results imply that infrared ear thermometers are not as accurate as rectal thermometers, this study has its limitations. First, it is a meta-analysis, meaning that the researchers pooled and analyzed data from many studies. Because studies are designed differently, meta-analyses lack a certain degree of precision, though they are useful in drawing general conclusions from many similar studies. Second, the settings and modes of the infrared ear thermometers used in these studies vary from one manufacturer to another. This variability dilutes the strength of these findings. Third, we know nothing about the calibration of the thermometers used, the depth of thermometer placement, and the time delay between the two temperature measurements—all factors that could affect the resulting temperature measurements.
Does this mean you shouldn’t use an infrared ear thermometer on your child? Not necessarily. This study simply suggests that rectal temperature may be a more accurate measure of core body temperature. However, other research has suggested that infrared ear thermometers yield temperature measurements equal to those of rectal thermometers.
If your child is ill and you can’t get a rectal temperature (which is not uncommon), measuring ear temperature with an infrared thermometer is better than getting no temperature measurement at all. A common problem with ear temperatures is improper positioning of the infrared device in the ear canal. Be sure to follow the instructions carefully and take several readings in rapid succession to make sure they are reasonably consistent. And don’t forget you can use an oral thermometer if your child is old enough to safely have the thermometer in his or her mouth. This study, however, did not assess the agreement between temperatures taken at the mouth and the rectum.
Craig JV, Lancaster GA, Taylor S, Williamson PR, Smyth RL. Infrared ear thermometry compared with rectal thermometry in children: a systematic review.
Akinyinka OO. Infrared ear thermometry versus rectal thermometry in children.
Last reviewed Aug 29, 2002 by Richard Glickman-Simon, MD
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