Non-contact infrared thermometers compared with current approaches in primary care for children aged 5 years and under: a method comparison study
Authors: Van den Bruel Ann , Verbakel Jan , Wang Kay , Fleming Susannah , Holtman Gea , Glogowska Margaret , Morris Elizabeth , Edwards George , Abakar Ismail Fatene , Curtis Kathryn , Goetz James , Barnes Grace , Slivkova Ralitsa , Nesbitt Charlotte , Aslam Suhail , Swift Ealish , Williams Harriet , Hayward Gail 
Published: October 2020

Background
Current options for temperature measurement in children presenting to primary care include either electronic axillary or infrared tympanic thermometers. Non-contact infrared thermometers could reduce both the distress of the child and the risk of cross-infection.

Objectives
The objective of this study was to compare the use of non-contact thermometers with the use of electronic axillary and infrared tympanic thermometers in children presenting to primary care.

Design
Method comparison study with a nested qualitative study.

Setting
Primary care in Oxfordshire.

Participants
Children aged ≤ 5 years attending with an acute illness.

Interventions
Two types of non-contact infrared thermometers [i.e. Thermofocus (Tecnimed, Varese, Italy) and Firhealth (Firhealth, Shenzhen, China)] were compared with an electronic axillary thermometer and an infrared tympanic thermometer.

Main outcome measures
The primary outcome was agreement between the Thermofocus non-contact infrared thermometer and the axillary thermometer. Secondary outcomes included agreement between all other sets of thermometers, diagnostic accuracy for detecting fever, parental and child ratings of acceptability and discomfort, and themes arising from our qualitative interviews with parents.

Results
A total of 401 children (203 boys) were recruited, with a median age of 1.6 years (interquartile range 0.79–3.38 years). The readings of the Thermofocus non-contact infrared thermometer differed from those of the axillary thermometer by –0.14 °C (95% confidence interval –0.21 to –0.06 °C) on average with the lower limit of agreement being –1.57 °C (95% confidence interval –1.69 to –1.44 °C) and the upper limit being 1.29 °C (95% confidence interval 1.16 to 1.42 °C). The readings of the Firhealth non-contact infrared thermometer differed from those of the axillary thermometer by –0.16 °C (95% confidence interval –0.23 to –0.09 °C) on average, with the lower limit of agreement being –1.54 °C (95% confidence interval –1.66 to –1.41 °C) and the upper limit being 1.22 °C (95% confidence interval 1.10 to 1.34 °C). The difference between the first and second readings of the Thermofocus was –0.04 °C (95% confidence interval –0.07 to –0.01 °C); the lower limit was –0.56 °C (95% confidence interval –0.60 to –0.51 °C) and the upper limit was 0.47 °C (95% confidence interval 0.43 to 0.52 °C). The difference between the first and second readings of the Firhealth thermometer was 0.01 °C (95% confidence interval –0.02 to 0.04 °C); the lower limit was –0.60 °C (95% confidence interval –0.65 to –0.54 °C) and the upper limit was 0.61 °C (95% confidence interval 0.56 to 0.67 °C). Sensitivity and specificity for the Thermofocus non-contact infrared thermometer were 66.7% (95% confidence interval 38.4% to 88.2%) and 98.0% (95% confidence interval 96.0% to 99.2%), respectively. For the Firhealth non-contact infrared thermometer, sensitivity was 12.5% (95% confidence interval 1.6% to 38.3%) and specificity was 99.4% (95% confidence interval 98.0% to 99.9%). The majority of parents found all methods to be acceptable, although discomfort ratings were highest for the axillary thermometer. The non-contact thermometers required fewer readings than the comparator thermometers.

Limitations
A method comparison study does not compare new methods against a reference standard, which in this case would be central thermometry requiring the placement of a central line, which is not feasible or acceptable in primary care. Electronic axillary and infrared tympanic thermometers have been found to have moderate agreement themselves with central temperature measurements.

Conclusions
The 95% limits of agreement are > 1 °C for both non-contact infrared thermometers compared with electronic axillary and infrared tympanic thermometers, which could affect clinical decision-making. Sensitivity for fever was low to moderate for both non-contact thermometers.

Future work
Better methods for peripheral temperature measurement that agree well with central thermometry are needed.

Trial registration
Current Controlled Trials ISRCTN15413321.

Funding
This project was funded by the National Institute for Health Research (NIHR) Health Technology Assessment programme and will be published in full in Health Technology Assessment; Vol. 24, No. 53. See the NIHR Journals Library website for further project information.