Accuracy of Different Types of Thermometers

Marilyn W. Edmunds, PhD, CRNP


April 20, 2010

Accuracy of Non-Contact Infrared Thermometry Versus Rectal Thermometry in Young Children Evaluated in the Emergency Department for Fever

Fortuna EL, Carney MM, Macy M, Stanley RM, Younger JG, Bradin SA
J Emerg Nurs. 2010;36:101-104


Oral and rectal temperatures are the most reliable predictors of core body temperature, but measuring these temperatures in children under 4 years of age is often difficult. Currently the rectal temperature is the clinical standard for small children. Axillary and aural thermometry may be less invasive, but previous research has shown that temperature measurements by these methods are not sufficiently accurate or reliable to use in situations when the child's temperature will determine treatment. In fact, 1 study showed that tympanic infrared thermometry fails to diagnose fever in 3-4 of 10 febrile children.

Study Summary

This study compared the accuracy of a noncontact infrared thermometer, used on the forehead, with that of a rectal thermometer in young children.

The study sample included 200 patients, age 1 month to 4 years, seen in a busy emergency department. Each child had simultaneous rectal thermometry and midforehead noncontact infrared thermometry measurements. Clinical data that were collected included chief complaint, list of recently administered antipyretic agents, and ambient temperature at the time of body temperature measurement.

Linear models were used to assess agreement between the 2 temperatures recorded with different techniques, as well as to determine whether the variation in infrared thermometry measurement differed from rectal temperature measurement. Multivariate linear models were used to evaluate the effect of clinical variables and ambient temperature.

A linear relationship between rectal and infrared temperature measurements was observed; however, no agreement was found between these 2 tests. The coefficient of determination (r2) value between the 2 measurements was only 0.48 (P < .01). The statistics showed that the infrared thermometer tended to overestimate the temperature of afebrile children and underestimate the temperature of febrile patients (P < .01). Ambient temperature and child age did not affect the accuracy of the device.

In this study, noncontact infrared thermometry did not agree well with rectal thermometer readings. The authors concluded that, "The agreement between the 2 methods was not sufficiently strong to recommend the use of the tested infrared device in clinical practice."

This simple, objective, tidy study addressed an important topic. Surprisingly, in many places in the world, axillary temperatures continue to be used because they are perceived to be the "cleanest" way of assessing temperature. However, many institutions also have policies about vital signs and how they are taken that may not be based on reliable evidence.

Although it is especially difficult to measure temperature in children, temperature measurement in adults can also be a challenge. Not infrequently, nurses comment that temperature readings are at variance with what they would have anticipated on the basis of clinical assessment. This research suggests that when these discrepancies occur, nurses should perhaps consider retaking the temperature, using another measurement method instead of simply considering the first reading an unusual finding.

We also might stop feeling sorry for all the poor, developing countries that don't have access to our high-technology devices for measuring temperature. The cheap and reliable rectal thermometer continues to be the standard for children.



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