What is the accuracy of no-touch (infrared) thermometers compared to axillary temperature measurements?

Accuracy of No-Touch (Infrared) Thermometers Versus Axillary Temperature

No-touch infrared thermometers (temporal artery thermometers) and axillary measurements are both unreliable and should not be used when accurate temperature measurement matters clinically. 1

Direct Comparison and Guideline Recommendations

Both no-touch infrared thermometers and axillary measurements are explicitly recommended against in critical care settings by the Society of Critical Care Medicine and Infectious Diseases Society of America. 1 The 2023 guidelines specifically state that noninvasive temporal artery thermometers (no-touch infrared devices) and axillary measurements should not be relied upon, grouping them together as the least reliable methods available. 1

Key Evidence on Accuracy

• Temporal artery (no-touch) thermometers have not been reliable when compared to core body temperature measurements, with estimates influenced by environmental temperature and sweating. 1

• Axillary measurements consistently underestimate core temperature by 1.5-1.9°C compared to more accurate methods and show variability up to almost 1°C. 1

• Both methods are poor screening tools for monitoring temperature in any clinical setting where accuracy matters for diagnosis or management decisions. 1

Hierarchy of Temperature Measurement Accuracy

The 2023 Critical Care Medicine guidelines establish a clear hierarchy from most to least accurate: 1

1. Most accurate (gold standard): Intravascular thermistors (pulmonary artery catheter), bladder catheter thermistors, esophageal thermistors
2. Acceptable alternatives: Rectal thermometers (though a few tenths of a degree different and not predictably consistent), oral thermometers (for alert, cooperative patients)
3. Unreliable and not recommended: Tympanic membrane infrared thermometers, temporal artery (no-touch) thermometers, axillary measurements, chemical dot thermometers

Clinical Implications

• When comparing the two methods in question: Neither no-touch infrared thermometers nor axillary measurements should be considered acceptable alternatives to each other, as both are fundamentally unreliable. 1

• Temperature discrepancies can be 1-2 degrees from actual core body temperature with peripheral and infrared methods, which can lead to missed diagnoses of fever or hypothermia. 1

• Missing fever or hypothermia has mortality implications: Patients with serious infections may be euthermic or hypothermic, and inaccurate temperature measurement could delay recognition and treatment of life-threatening conditions. 1

Common Pitfalls

• Assuming any temperature measurement is "close enough": In critically ill patients or those where infection is suspected, inaccurate temperature measurement can lead to delayed diagnosis and treatment, directly impacting mortality. 1

• Using convenience over accuracy: While no-touch thermometers are convenient and reduce infection transmission risk, this convenience comes at the cost of clinical reliability. 1

• Not documenting the measurement site: The site of temperature measurement must be recorded with the temperature value to allow proper interpretation. 1

Practical Recommendation

If neither central thermometry nor oral/rectal measurements are feasible, recognize that any temperature obtained from no-touch infrared or axillary methods is unreliable and should not guide clinical decisions. 1 In such cases, clinical assessment based on other signs of infection (hypotension, tachycardia, altered mental status, laboratory abnormalities) becomes paramount rather than relying on the temperature value itself. 1