Peripheral Thermometers Lack Accuracy

Diana Swift

November 16, 2015

Peripheral thermometers lack clinically acceptable accuracy and should not be used when precise measurement of core body temperature will influence clinical decisions, according to a meta-analysis published online November 16 in the Annals of Internal Medicine.

"At extremes of body temperature, peripheral temperature measurements may be as much as 1 to 2 degrees higher or lower than actual body temperature," write lead author Daniel J. Niven, MD, an intensive care physician in the Department of Critical Care Medicine at the University of Calgary, Alberta, Canada, and colleagues.

"Peripheral thermometers therefore represent a poor screening tool for detecting temperature abnormalities."

The researchers analyzed 75 prospective studies from 21 countries (8682 patients, 43% pediatric). The median age of adults was 61 years, and for children it was 16 months.

The studies all compared the accuracy of peripheral (tympanic membrane, temporal artery, axillary, or oral) thermometers with central (pulmonary artery catheter, urinary bladder, esophageal, or rectal) thermometers.

The authors note that the majority of studies were at risk for high or uncertain patient selection bias (74%) or index test bias (67%), and 53% were conducted more than 10 years ago. The studies were also widely heterogeneous, with an interstudy heterogeneity (I 2) of 95.7% (P < .001), and high-quality data are limited for some measurement techniques.

Compared with central devices, peripheral thermometers had pooled 95% limits of agreement outside the predefined clinically acceptable range (±0.5°C), especially among patients with fever (−1.44°C to 1.46°C for adults; −1.49°C to 0.43°C for children) and hypothermia (−2.07°C to 1.90°C for adults; no data for children). Only one study reported sensitivity and specificity for the detection of hypothermia.

Furthermore, sensitivity for the detection of fever was low, at 64% (95% confidence interval, 55% - 72%). Specificity was high, at 96% (95% confidence interval, 93% - 97%; I 2 96.3%; P < .001).

The researchers note that low-grade fever is a potentially important sign of infection in patients who may not manifest a typical infectious prodrome; for example, elderly patients or those with immune system impairments, connective tissue disease, or tumors.

"Given the excellent level of agreement between nonvascular central thermometers and the pulmonary artery catheter — the gold standard — clinicians should consider using central thermometers when accurate measurement of a patient's temperature will influence diagnosis and management," Dr Niven and associates write. They suggest that rectal thermometers could be used for most patients, whereas bladder thermometers could be used for those requiring a bladder catheter.

When central thermometers should not be used (eg, in patients with neutropenia) electronic oral thermometers (for adults) or tympanic membrane thermometers (for adults and children) that are calibrated before use seem to be the best alternatives.

This study received no specific funding. The authors have disclosed no relevant financial relationships.

Ann Intern Med. Published online November 16, 2015.

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