The clinical utility of the rectal-skin temperature difference in the assessment of young infants

Abstract

Objective: Previous studies have suggested that the degree of difference between rectal temperature and peripheral skin temperature [rectal-skin temperature difference (RSTD)] is predictive of serious illness in young infants. The authors sought to determine the clinical utility of the RSTD in the outpatient evaluation of infants up to 2 months of age for serious infectious illness (SII). Methods: Simultaneous rectal and skin (anterior mid-lower leg) temperatures were recorded for all infants ≤2 months of age seen in the ED over a one-year period. The physician's clinical assessment, rectal temperature, skin temperature, laboratory results, and final diagnoses were also recorded. The RSTD (rectal temperature - skin temperature) was calculated for each infant. Final diagnoses were recorded and classified as SII or nonserious illness (NSI). Mean RSTD for each group was calculated and data were analyzed by the Wilcoxon rank sum test and multivariate regression model Results: A total of 601 infants [mean age of 28 days (range 2-65 days)] were enrolled. Nine percent (57 of 601) of infants had SII. Forty percent (23 of 57) of infants with SII were febrile, and 60% (34 of 57) were afebrile. The mean RSTD of febrile infants with SII was 5.8 ± 1.7°C (range 3.2- 9.7°C) and 5.3 ± 1.4°C (range 3.0-7.6°C) for febrile infants with NSI. The mean RSTD of afebrile infants with SII was 4.8 ± 1.8°C (range 2- 12.5°C) and 4.4 ± 1.5°C (range 0.04-10.9°C) for afebrile infants with NSI. The RSTD was not associated with SII in either febrile or afebrile infants (p > 0.05, Wilcoxon rank sum test). A multivariate logistic regression model of age, rectal temperature, and RSTD suggested an independent association of rectal temperature with SII (p < 0.0001), but none between age or RSTD and SII (p > 0.05). Conclusion: Once the rectal temperature is known, the RSTD is not a clinically useful test in the evaluation of young infants for serious infectious illness.