Exercise: forehead temperature

This website is for students following the M.Sc. in Evidence Based Practice at the University of York.

The following is the abstract of a paper:

Background: Noncontact forehead temperature measurement by handheld infrared thermometer was used as a screening tool for fever. However, the accuracy data and normal range of forehead temperature determined by this method were not available.

Methods: The temperature readings from 3 handheld infrared thermometers were validated against an electronic thermometer. Normal range of forehead temperature was determined by measuring the forehead temperature in 1000 apparently healthy subjects.

Results: Significant differences were detected in readings obtained by the 3 different handheld infrared thermometers (analysis of covariance, P < 0.001). The most accurate one was chosen, and the normal range of forehead temperature in 1000 subjects detected by this method was 31.0°C to 35.6°C.

Conclusions: Our study shows that commercially available, handheld infrared thermometers require individual validation. Forehead temperature in excess of 35.6°C is suggestive of fever. Further studies are required to confirm accuracy of this value in detecting fever.

(Source: Ng DK, Chan C, Chan EY, Kwok K, Chow P, Lau W, Ho JC. A brief report on the normal range of forehead temperature as determined by noncontact, handheld, infrared thermometer. American Journal of Infection Control 2005; 33: 227-229.)

The sample for the normal range was found as follows: 'Staff and visitors of our hospital were invited to join the study. Subjects aged over 18 years and below 65 years were enrolled in this study. Individuals with a history of fever, ingestion of antipyretic, and immunization within the preceding 7 days or those with symptoms such as cough, runny nose, or sore throat were excluded.'

The authors produced the following graph for forehead temperature (FT) in 1000 apparently healthy adults:

They wrote that 'The normal range for FT was 31.0°C to 35.6°C (87.8°F to 96.1°F) (mean ± 1.96° standard deviation). Those with FT higher than 35.6°C were statistically abnormal.'

Questions about this abstract:

1. What is meant by 'the normal range of forehead temperature'?
   Check suggested answer.
2. Upon what assumptions does their calculation of the normal range depend? Do you think that these assumptions are met?
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3. In what sense are people with forehead temperature higher than 35.6°C statistically abnormal?
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4. What is the evidence for their conclusion that 'Forehead temperature in excess of 35.6°C is suggestive of fever.'?
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5. What kind of study would be better to draw this kind of conclusion?
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6. What measurement problem does the histogram show? (Relates to the measurement lecture in the Research Methods module, but irresistable!)
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Last updated: 2 March, 2007.

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