The comparison of axillary and rectal temperature in the premature infants under 32 weeks of gestation

The average AT and RT measurements were 36.52? and 36.71?, respectively. The axillary measurements were lower than the rectal measurements. The mean difference in the BT measurements (between the axillary and rectal measurements), which was attributed to the methods of measurement, was 0.183? (0.158–0.207?) and was statistically significant. In the subgroup analysis according to gestational age, the group of extremely preterm infants with a gestational age of < 28 weeks demonstrated an average difference of 0.188? between the AT and RT measurements (P = 0.013). In contrast, for the group of very preterm infants with a gestational age of 28–32 weeks, the mean difference was 0.180? (P < 0.0001). A stable, consistent, and significant difference in BT measurements of < 0.5? was observed according to the method of measurement in each group. The differences in the AT and RT measurements and the relationships between them were analyzed using correlation analysis. We identified a linear relationship between the differences in BT measurements between the two methods, which increased with increasing RT measurements. Furthermore, a slower rate of increase was observed in the AT measurements than in the RT measurements. We derived the following calibration formula to estimate the RT according to the AT: RT (?) = -4.033 + 1.116 × AT (?). Multivariate analysis was performed to determine the effects of environmental factors (e.g., incubator temperature, humidity, and type of ventilatory support) on the differences in BT measurements. We did not find any statistically significant correlation between any of these factors and the BT measurements.