Comparison of rectal and infrared ear temperatures in older hospital inpatients

OBJECTIVES: To assess the agreement between infrared emission detection (IR ED) ear and rectal temperatures and to determine the validity of IRED ear t hermometry in detecting rectal fever. DESIGN: Prospective, convenience sample, unblinded study. SETTING: An acute geriatric unit (teaching hospital) and a multidisciplinar y intensive care unit. PARTICIPANTS: The study included 45 inpatients (26 women and 19 men), aged 78.3 +/- 6.9 years, admitted over a 4-month period. Twelve of the patients were definitely infected. MEASUREMENTS: Sequential rectal (RT) and ear temperature (ET) measurements were performed using mercury-in-glass and IRED ear thermometers, respective ly. IRED ear temperatures were measured at both ears (unadjusted mode), wit h the highest of six ear temperatures considered the true value. RESULTS: Mean RT (37.39 degrees C +/- 0.52 degrees C) was significantly (P < .001) higher than mean ET (36.89 degrees C +/- 0.59 degrees C). A highly significant positive correlation was found between RT and ET (slope = 0.69; 95% CI, 0.52-0.86; P < .001; r = 0.78). The mean bias (mean of the differe nces) between RT and ET was 0.50 degrees C i 0.37 degrees C (95% CI, 0.41 d egrees C-0.59 degrees C), and the 95% limits of agreement -0.22 degrees C a nd 1.23 degrees C (95% CT, -0.38 degrees C to 1.39 degrees C). According to the standard criterion (RT greater than or equal to 37.6 degrees C), 14 pa tients were febrile. Using an optimum IRED ear fever threshold (37.2 degree s C), the sensitivity and specificity of IRED ear thermometry for predictin g rectal fever were 86% and 89%, respectively (positive predictive value, 8 0%; negative predictive value, 93%). CONCLUSIONS: The degree of agreement between rectal temperature and the hig hest of six IRED ear temperatures was acceptable. Using an optimal IRED ear fever threshold of 37.2 degrees C (99 degrees F), IRED ear thermometry had acceptable sensitivity and specificity for predicting rectal fever.