Comparison of rectal, axillary, and forehead temperatures.

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.