It is folly to believe that ear temperature and rectal temperature should agree in febrile patients except by chance. The time course for temperature change is different at different body sites and the rectal site is particularly slow to respond to changes. During periods of rapid temperature change (as in the febrile child), rectal temperature may actually change in a direction opposite core temperature changes. We have known this since Gerbrandy's elegant studies in the mid 1950's. We now have several recent studies in open heart surgery patients that demonstrate (again) that ear temperature more accurately tracks changes in core body temperature, while rectal lags by about 30 minutes.
Throw away your rectal thermometers. They are inaccurate, inappropriately invasive, and nonhygienic. As a diagnostic test, rectal temperature has horrible operator characteristics of very poor sensitivity and specificity for detection of bacterial disease.
Sorry for the soapbox, just finished a night shift.
JMHO, but, in this case, it is actually based on evidence (not like my usual ramblings).
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