Peripheral thermometers may inaccurately measure body temperature

1. From a systematic review and meta-analysis, peripheral thermometers had a high specificity for detecting fever, but their sensitivity was low.

2. Central thermometers, such as rectal, bladder and esophageal thermometers, had high accuracy for determining body temperature.

Evidence Rating Level: 1 (Excellent)

Study Rundown: Body temperature is a key indicator of illness, and thermometers are a ubiquitous item in home medicine cabinets and hospitals alike. However, although body temperature—and particularly the presence of fever—is essential for guiding medical decisions, there is a surprising lack of consensus on the accuracy of various methods to measure temperature. This study pooled data from several investigations of different types of thermometers, aiming to determine how accurate peripheral thermometers (those used outside the body, such as under the armpit or in the ear) and central thermometers (those placed in the rectum, bladder, or esophagus) were compared to a gold standard vascular thermometer (which measures temperature in the blood vessels). Remarkably, peripheral thermometers were highly inaccurate compared to central thermometers, with agreement between methods falling outside the pre-set acceptable cutoffs. Although peripheral thermometers were found to have a high specificity (they reliably confirmed that a patient had a fever), they were found to have low sensitivity (they were not reliable at ruling out fever). In contrast to peripheral thermometers, central thermometers were highly accurate at determining temperature. This analysis was limited by several factors relating to the studies it included; notably, there was significant heterogeneity in results from different studies, and there was some evidence of publication bias. Nevertheless, these results provide compelling evidence that peripheral thermometers inaccurately measure body temperature, and that central thermometers should be used when clinical decisions rely upon accurate temperature measurement.

Click to read the study published today in the Annals of Internal Medicine

Relevant Reading: Fever in Hospitalized Medical Patients: Characteristics and Significance

In-Depth [systematic review and meta-analysis]: This systematic review and meta-analysis analyzed results of 8,682 patients from 75 studies that compared the accuracy of peripheral and central thermometers. Studies of both children and adults were included. Peripheral measurement methods included tympanic membrane, axillary, temporal artery and oral thermometers; central measures included pulmonary artery catheters (which were defined as the gold-standard reference method, against which other thermometers were compared), rectal, bladder and esophageal thermometers. Overall, accuracy of peripheral thermometers fell outside a pre-defined acceptable limit of agreement of +/- 0.5 °C compared to central thermometers; accuracy of rectal, bladder and esophageal central thermometers fell within this acceptable limit of agreement compared to pulmonary artery thermometers. Sensitivity of peripheral thermometers to detect fever was only 64% (95%CI 55% to 72%), although specificity was 96% (95%CI 93% to 97%). Although central thermometers are already used routinely in some contexts (e.g., rectal temperature measurement in pediatric patients), this analysis argues for increased use of central temperature measurement whenever clinical decision-making depends upon accurate body temperature measurements.

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