Comparison of non-contact infrared skin thermometers

Abstract

Non-contact infra-red skin thermometers (NCITs) are becoming more prevalent for use in medical diagnostics. Not only are they used as an alternative means of estimating core body temperature but also to assess the diabetic foot for signs of inflammation prior to ulceration. Previous investigations have compared the performance of NCITs in a clinical setting against other gold standard methods. However, there have been no previous investigations comparing the performance of NCITs in assessing temperature measurement capability traceable to the International Temperature Scale of 1990 (ITS-90). A metrological assessment of nine common NCITs was carried out over the temperature range of 15–45 °C using the National Physical Laboratory’s blackbody reference sources to identify their accuracy, repeatability, size-of-source and distance effects. The results are concerning in that five of the NCITs fell far outside the accuracy range stated by their manufacturers as well as the medical standard to which the NCITs are supposed to adhere. Furthermore, a 6 °C step change in measurement error over the temperature range of interest for the diabetic foot was found for one NCIT. These results have implications for all clinicians using NCITs for temperature measurement and demonstrate the need for traceable calibration to ITS-90.

Keywords:

• Temperature
• thermometer evaluation
• calibration
• traceability

Acknowledgements

The study got kind contributions from Prof Michael Edmonds (King’s College Hospital NHS Foundation Trust), Dr Nina Petrova (King’s College Hospital NHS Foundation Trust), Prof Francis Ring (University of South Wales), Dr John Allen (Newcastle Upon Tyne Hospitals NHS Foundation Trust), Audrey MacDonald (Newcastle Upon Tyne Hospitals NHS Foundation Trust), Dr John Bevans (Pennine Acute Hospitals NHS Trust), Suhail Ainarkar (Pennine Acute Hospitals NHS Trust) and Benjamin Kluwe (University of South Wales).

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was funded by the NIHR Invention for Innovation programme (i4i), Grant reference II-LA-0813–20007 and National Institute for Health Research.