Comparison of rectal, axillary, and forehead temperatures
F. Shann and A. Mackenzie
Goroka Base Hospital, Papua New Guinea.
OBJECTIVE: To assess whether axillary and forehead temperatures accurately
reflect the rectal temperature (the criterion standard) DESIGN: Prospective
study with calculation of paired axillary-rectal and forehead-rectal
temperature differences and their SDs. SETTING: Referral hospital.
PARTICIPANTS: Convenience sample of 120 patients, with 20 patients in each
of six age groups (ie, < 1 month, 1 to 5 months, 6 to 11 months, 12 to
23 months, 2 to 14 years, and adults) RESULTS: In newborns, the rectal
temperature was equal to the axillary temperature plus 0.2 degrees C for
each week of age up to 5 weeks; forehead strip thermometers gave inaccurate
readings in this age group. In patients older than 1 month, the mean
difference (SD) between the rectal and axillary temperatures was 1.04
degrees C (0.45 degrees C); thus the axillary temperature was adjusted by
adding 1 degree C, and no adjusted axillary temperature differed from the
rectal temperature by more than 1 degree C. The mean difference (SD)
between the forehead temperature that was measured by the best forehead
liquid crystal strip thermometer (FeverScan) and the rectal temperature was
0.14 degrees C (0.60 degrees C); 10 forehead temperatures differed from the
rectal temperature by more than 1 degree C. CONCLUSIONS: Previous studies
that have suggested that axillary and forehead temperatures do not provide
a reliable guide to the rectal temperature have all used inappropriate
methods of analysis (correlation coefficients or sensitivity and
specificity); previous studies that have based their conclusions on the
correct method of analysis (paired differences and their SDs) have all
found that the axillary temperature gives a good indication of the rectal
temperature. The axillary temperature can be measured safely at any age,
and the axillary temperature plus 1 degree C is a good guide to the rectal
temperature in patients older than 1 month. Forehead strip thermometers are
easy to use, but they do not estimate the rectal temperature as accurately
as the axillary temperature does.
