Evaluation of a new thermometer for rapid axillary temperature measurement in preterm infants

Mercury-in-glass thermometers are considered the "gold-standard" for temperature measurements, but require at least 4 minutes for accuracy. Electronic thermometers sample temperature measurements over a shorter period. The objective of this study was to evaluate the accuracy and reproducibility of the Penguin (Medisim, Jerusalem, Israel) and the IVAC (San Diego, CA) Temp plus II thermometers in preterm infants. Axillary temperature was obtained in 50 thermally stable preterm infants each time with the mercury-in-glass, the IVAC, and the Penguin thermometers. Analysis of variance F-test, and linear regression analyses were used to test correlation of each electronic thermometer with the mercury-in-glass one, and the effect of body weight. Temperature measurement taken with the Penguin thermometer was significantly higher than that measured with the two other ones, p < 0.001. The differences in means and in variances were not significantly different between IVAC and mercury-in-glass, while the variance of the Penguin measurement was higher than that of the two other instruments (p < 0.001). The IVAC instrument correlated more tightly with the mercury-in-glass (r = 0.89, p < 0.001) than did the Penguin (r = 0.54, p < 0.001). There was an inverse correlation between the deviation of the Penguin measurement from the mercury-in-glass and the weight of the patient (p < 0.08), while no significant correlation was found between the deviation of the IVAC measurement from the mercury in glass and the patient's weight (p = 0.56). Measurements of axillary temperature using the Penguin thermometer in incubated preterm infants are less accurate and less reproducible than those obtained using the IVAC or the glass thermometers.