A5V4d

Thermometers and the detection of fever
reported to be comparable with other thermometers used in the axilla. In the one study to compare
the ability to detect fever against rectal temperature, the sensitivity was 68%. (EL II)
Tympanic temperature (by infrared thermometer)
Tympanic measurement differs on average from body temperature by 0.3°C. From EL Ib and EL II
studies the difference between tympanic temperature and body temperature can be up to 0.74°C
below to 1.34°C above and this varies with age, mode, environment temperature and device. The
sensitivity to detect fever ranged from 51% to 97% in these studies.
Some studies reported that tympanic measurements are difficult or inaccurate in infants under the age
of 3 months. Other studies reported that the technique could be used in infants of all ages, including
neonates. A statement that tympanic measurements should not be used in infants under the age of
3 months was put to the Delphi panel. Consensus was not attained.
Forehead temperature (by chemical thermometer)
Data on the measurement of forehead temperature is sparse. The limited data suggests that forehead
measurement appears to be inaccurate (underestimates body temperature by 1.2°C on average).
(EL II) Forehead thermometers may be poor at detecting fever (sensitivity 27–88%). (EL II)
Temporal artery temperature (by infrared thermometer)
Measurement of temporal artery temperature has not been extensively studied. The available data
suggest this technique has fair sensitivity (81%) to detect fever. (EL III)
Health economics profile
Cost analysis of thermometers was undertaken for this guideline (chapter 11). The analysis was
based on the data from hospital setting as regards the annual number of measurements. 85 The results
of the analysis are summarised in Table 5.3. The results are discounted to show the present value of
costs which accrue in the future (up to 10 years). The analysis showed that the contact/electronic
thermometers are the least costly option when staff costs are not included in the analysis. When the
staff cost are included, the total cost of electronic/compact, contact/compact electronic and tympanic
thermometers are comparable. Contact/electronic thermometers have a high purchase price but the
fact that they can be used repeatedly means that they may be less costly per test than the chemical
thermometers, which have a low purchase price but can be used only once (or can be reused only a
limited number of times). Since the cost per test is dependent on the volume of tests undertaken,
chemical thermometers may be a better use of resources than either electronic thermometer in very
low volume settings, such as some primary care providers.
GDG translation
The GDG noted that the alternatives to oral and rectal thermometers can all give inaccurate readings
and have variable sensitivity in detecting fever. Taking temperatures by the axillary route using an
electronic or chemical dot thermometer underestimates body temperature by 0.5°C on average.
Tympanic temperatures measured with an infrared thermometer differ from body temperature by
0.3°C on average. The GDG noted that these three types of measurements had not been compared
with each other and therefore decided that they could not recommend one type over another. Data
from neonates suggests that axillary measurements are more accurate in this age group and it was
therefore decided to recommend this route at that age.
The GDG was aware that some authorities suggest that tympanic measurements are unreliable or
impossible to perform in infants under the age of 3 months. The evidence was inconclusive on this
issue and when the question was put to the Delphi panel there was no consensus. Accordingly, the
GDG felt that they could not suggest age limits on the use of tympanic thermometers. The GDG
considered that more research was needed in this area. Moreover, it would be helpful if direct
comparisons were made between all of the different thermometers that were recommended for use in
young children.
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