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 Table of Contents  
ORIGINAL ARTICLE
Year : 2020  |  Volume : 7  |  Issue : 4  |  Page : 256-260

Efficacy of industrial-grade infrared noncontact temperature recording device for fever screening during coronavirus pandemic


1 Department of Anaesthesiology and Critical Care, Armed Forces Medical College, Pune, Maharashtra, India
2 Department of Internal Medicine, Armed Forces Medical College, Pune, Maharashtra, India
3 Department of Community Medicine, Armed Forces Medical College, Pune, Maharashtra, India

Date of Submission10-May-2019
Date of Decision11-Jun-2020
Date of Acceptance24-Aug-2020
Date of Web Publication8-Apr-2021

Correspondence Address:
Vishal Mangal
Department of Internal Medicine, Armed Forces Medical College, Pune - 411 040, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/cjhr.cjhr_50_20

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  Abstract 


Background: The World Health Organization declared COVID-19 “a pandemic” on March 11, 2020. An essential preventive and screening strategy adopted was temperature screening at various public places such as airports and hospitals with devices like handheld, noncontact infrared thermometers. Before this pandemic, the industrial thermometers have never been used in health-care settings. The study was conducted to compare temperature readings of these industrial-grade infrared noncontact handheld thermometers with a digital thermometer. Materials and Methods: Three Testo® industrial-grade infrared noncontact thermometer (IGNCT) and Dr. Trust digital thermometer were used on 117 individuals for recording temperature. The average of three readings was taken for each instrument by a single investigator. Results: Out of 117 individuals, 14 (11.9%) were febrile. The Pearson correlation values between the digital thermometers varied from 0.3 to 0.42. The reliability, as measured by the intraclass correlation, was poor (0.16-“0.4). The area under the curve for IGNCT devices varied from 76% to 84%. Conclusion: Industrial-grade infrared noncontact temperature (IGNCT) recording devices with its no-touch technique to measure temperature while maintaining distance may be useful in a pandemic situation. However, the higher the area under the curve, the better it is. In a large cohort, 20% will be misclassified, and in absolute terms, they may be translated into large numbers. Hence, there is a case for better devices having an area under the curve of nearly 100% for the screening of population. The role of IGNCT devices for the screening of individuals to identify cases of febrile illness is limited owing to its poor reliability and unacceptable area under the curve for screening large populations.

Keywords: COVID-19, industrial-grade, infrared, noncontact thermometer, screening, temperature


How to cite this article:
Kaur KB, Singhal A, Yadav AK, Mangal V, Jain R, Kumar S. Efficacy of industrial-grade infrared noncontact temperature recording device for fever screening during coronavirus pandemic. CHRISMED J Health Res 2020;7:256-60

How to cite this URL:
Kaur KB, Singhal A, Yadav AK, Mangal V, Jain R, Kumar S. Efficacy of industrial-grade infrared noncontact temperature recording device for fever screening during coronavirus pandemic. CHRISMED J Health Res [serial online] 2020 [cited 2021 Apr 19];7:256-60. Available from: https://www.cjhr.org/text.asp?2020/7/4/256/313175




  Introduction Top


In the 2019 year-end, China testified a large number of pneumonia cases, which were later diagnosed as severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on December 31, 2019.[1],[2],[3] In view of the widespread transmission of COVID-19 worldwide, the World Health Organization declared COVID-19 “a pandemic” on March 11, 2020.[4] The first case in India was diagnosed on January 30, 2020. Till April 19, 2020, India had reported 17,305 confirmed cases of COVID-19.[5] Coronavirus affected patients frequently present with the symptoms of cough, fever, and shortness of breath.[6]

The different preventive strategies were adopted by different countries such as cancellation of domestic and international travel, banning mass gatherings, implementing complete lockdown, and self-monitoring of symptoms. An essential preventive and screening strategy adopted was temperature screening at various public places such as airports and hospitals with devices like handheld, noncontact infrared thermometers, and walk-in thermal scanners. A large-scale program to identify and screen the persons already exposed to COVID-19 by temperature screening should help control the virus.[7],[8] The Food and Drug Administration (FDA) considers a telethermographic system to be a medical device when it is intended for a medical purpose, such as a measure of the self-emanating infrared radiation that reveals the relevant temperature variations of the body surfaces.[9] These telethermographic systems are indicated for initial temperature assessment for triage use in high-throughput areas (e.g., airports, businesses, warehouses, and factories) and in settings where other temperature assessment products may be in short supply.[10] The mass temperature screening by conventional methods is a very challenging and time-consuming task. The available scientific literature supports the use of telethermographic systems in the context of initial human temperature measurement during mass screening of infectious disease pandemics.[9],[10],[11],[12],[13] Hence, using noncontact infrared thermometers presents an acceptable solution as it will take less time to screen and eliminate the risk of SARS-CoV-2 transmission from one person to other during temperature screening.

The increased demand and restricted mobility due to lockdown made the supplies, whether it is the masks, personal protective equipment, or noncontact thermometers, scarce. In view of increasing demand, industrial-grade infrared noncontact thermometers (IGNCT) came into the picture for use.

In 1990s after the discontinuation of conventional mercury thermometers, many different temperature recording devices came in use into clinics, hospitals, and homes. Subsequently, different types of digital and infrared tympanic thermometers were used by many institutions. The tympanic infrared thermometer frequently used in inpatient care has been shown to correlate with core body temperature.

Industrial/environmental infrared (IR) thermometers measure surface temperatures over an extensive temperature range to suit a multitude of industrial applications. Temperature measured in this category of thermometers can range from −60 to over 500°C. The extent of this range means there is a trade-off in measurement accuracy.

Industrial/environmental IR thermometers have an error factor that averages around ±1°C-“1.5°C, which is more than satisfactory for the majority of industrial/environmental applications.

In contrast, the output of medical IR thermometers must be far more accurate, and the temperature range need only shoulder the expected bodily temperatures of a human. Medical IR thermometers have a range somewhere in the field of 32°C-“42.5°C, and you can expect a level of accuracy of ±0.1°C. Considering that the difference between well and unwell is only a couple of degrees, an industrial thermometer is an inappropriate tool.[14]

In our center, three IGNCT devices were bought and were deployed for use in screening. Before this pandemic, the industrial thermometers have never been used in health-care settings. It was planned to study the accuracy of these thermometers as compared to the digital thermometers and validate their readings.


  Materials and Methods Top


To validate the efficacy of IGNCT in a health-care setting, three Testo-835 thermometers and a digital thermometer were used. Dr. Trust digital thermometer was used in the study. This appliance conforms to the following standards: EN 12470-3 clinical thermometers part 3, ISO 80601-2-56 medical electrical equipment part 2-56, EN 60601-1-11 medical electrical equipment part I-“II, and complies with the requirements of En 60601-1-2 (EMC), IEC/EN 60601-1 (safety) standards. Moreover, the manufacturer is ISO 13485 certified. Specifications of the digital thermometer are depicted in [Table 1]. IGNCT device used in the study was Testo 835. The detailed specifications are given in [Table 2]. For a digital thermometer, the probe was placed in the armpit, and the arm was kept firmly pressed at the site. The degree sign flashes through the testing process. When flash stops, an alarm beeps for 10 s, and the measured reading appears on the screen simultaneously. The manufacturer recommends that the device should be kept in the armpit for 5 min. For the IGNCT Testo 835, the device was held 3 cm away from the forehead, and the reading was noted. All the temperature measurements were taken by a single researcher to avoid interobserver bias. For every patient, the temperature was measured in random order with all the four devices, and groups were made as digital thermometer D1, Noncontact thermometer device number 1 (NCT1), Noncontact thermometer device number 2 (NCT2), and noncontact thermometer device number 3 (NCT3). Three recordings were taken with each device at every time, and the mean temperature was recorded. The study was approved by the institutional ethics committee vide certificate number: IEC/2020/178.
Table 1: Specifications of Dr. Trust digital thermometer

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Table 2: Specifications of industrial-grade handheld noncontact thermometer Testo 835

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The sample size was calculated with the following assumptions that the minimum interclass correlation (ICC) that data should be able to detect is 0.3, with two observations, alpha as 0.05 and power as 80%. The calculated sample size was 83. However, we took a total of 117 individuals in our study. All the admitted patients who were more than 18 years of age with or without fever and gave informed written consent were included in the study. Data were analyzed using standard deviation for quantitative variables and frequency and percentages for qualitative data. The scatter diagram was made [Figure 1]. The intraclass correlation was calculated. The data were collected and compiled on Microsoft Excel version 2019 and analyzed using StataCorp. 2013. Stata Statistical Software: Release 13. College Station, TX: StataCorp LP.
Figure 1: Scattered box plot showing various records of temperature in febrile patient and nonfebrile patient groups. Mean CT: Mean of temperature by the digital thermometer, Mean NCT1: Mean of temperature recorded by noncontact thermometer device number 1, Mean NCT2: Mean of temperature recorded by noncontact thermometer device number 2, Mean NCT3: Mean of temperature recorded by noncontact thermometer device number 3

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  Results Top


There were a total of 117 participants in the study. A total of 103 (88.1%) had normal body temperature, and 14 (11.9%) had the fever (defined as temperature >99.9°F). Out of these participants, 9 (7.7%) were female. 46 (39.3%) participants belonged to 30-39 years of age, the 33 (28.2%) to 20-“29 years of age, and only 11 (9.4%) were above 50 years of age. The mean value of temperature by the digital thermometer was 97.03°F (standard deviation [SD] = 1.44), and the mean of temperature by three noncontact thermometers was 94.2°F (SD = 1.92), 95.2°F (SD = 1.89), and 94.7°F (SD = 1.86), respectively. NCT1 gave 1 reading, which was higher than the axillary temperature by a digital thermometer. NCT2 gave 12 readings, which were higher than the axillary temperature by a digital thermometer, and NCT3 gave 5 readings, which were higher than the axillary temperature by a digital thermometer.

The result of the scatter plot showed a correlation among the noncontact thermometer. However, the strength of the correlation with the digital thermometer was only moderate [Table 3]. The agreement between the readings was observed by the Bland-“Altman plot [Figure 2]. The consistency or reliability of readings was assessed using ICC [Table 3]. The values <0.5 reflect poor consistency in ICC.
Table 3: Interclass correlation values of digital thermometer versus noncontact thermometer

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Figure 2: Interclass corelationship with the degree of agreement in various types of thermometers used. (a) No fever by noncontact thermometer device number 1, (b) no fever by noncontact thermometer device number 2, (c) no fever by noncontact thermometer device number 3, (d) fever by noncontact thermometer device number 1, (e) fever by noncontact thermometer device number 2, (f) fever by noncontact thermometer device number 3

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The receiver operating characteristic (ROC) curve for all three devices was drawn using the reading of a digital thermometer as the gold standard. The same is shown in [Figure 3]. The area under the curve for NCT1, NCT2, and NCT3 was 0.76, 0.83, and 0.84, respectively.
Figure 3: Receiver operating characteristic curve of all the readings

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  Discussion Top


The pulmonary artery catheter, which measures blood temperature, is considered the gold standard for measuring core temperatures.[15] Although the handheld cutaneous IR thermometer is popularly used to screen large cohorts as it is portable, does not require contact, and does not cause discomfort to the individual being assessed, however there are little data to support its use. Most of the studies done on the use of cutaneous IR thermometers' evaluation for measuring temperature as per the International Temperature Scale of 1990, showed the accuracy as outside the range as stated by the manufacturers and the medical standard.[16] The handheld cutaneous IR thermometer was less accurate than the tympanic thermometer and other IR thermal systems for temperature measurements and fever detection. Studies in the past on tympanic temperature readings showed that they varied from core temperature readings by an average of 0.9°C, but the variability could be significant up to 2.5°C in some patients.[17]

IGNCT has never been used to monitor human body temperature, however during the present COVID-19 pandemic, due to sudden increase in the demand and unavailability of FDA-approved noncontact temperature monitoring devices due to lockdown, our institution bought three IGNCT devices for screening the individuals entering our hospital for COVID-19. Before we could use these devices on the ground, we tested them on healthy volunteers and fever patients. Despite the fact that all three devices were from the same manufacture, they gave different readings. The difference between mean temperature recorded by digital thermometer and NCT1, NCT2, and NCT3 was −2.61 ± 1.59, −1.71 ± 1.60, and −2.25 ± 1.61, respectively, and the difference in mean temperature was more in the case of fever patients.

In addition, its performance is operator dependent, as the thermometer is aimed at the temple or forehead, and distance between the thermometer and skin may affect its accuracy.[16] It is not unlikely that suboptimally trained operators, shying away from close contact with those being screened, hold the thermometer further away than the required proximity and thus compromise its effectiveness.

The reliability of the instrument was poor, as indicated by the poor ICC values of the instruments. In our study, the trained person took the readings. However, reliability is likely to be lower if untrained persons are used to recording the temperature.

ROC curve indicates that the NCTs have an area under the curve of around 80% and hence can classify as many people correctly as febrile or afebrile. This, coupled with its no-touch technique to measure temperature while maintaining distance, may be useful in a pandemic situation. However, the higher the area under the curve, the better it is. In a large cohort, 20% will be misclassified, and in absolute terms, they may be translated into large numbers. Hence, there is a case for better devices having an area under the curve of nearly 100% for the screening of population.

The earliest pandemic of Spanish flu in 1918 caused at least 50 million deaths worldwide.[18] The infrared thermometers were not available at that time as they were developed in 1960s.[19] During the 2002-“2003 SARS minipandemic, there were a total of 8096 probable cases and 774 deaths.[20] The Ebola virus disease outbreaks in 2014-“2016 in Africa caused around 28,000 cases and 11,323 deaths.[21] All these outbreaks were limited with few thousand cases, and there never arose the need to use industrial-grade infrared temperature screening devices, however medical IR temperature screening devices were used in these infectious disease outbreaks.[11],[12],[13] The strength of the study is that a single investigator has done all the measurements, thus preventing the interrater bias. This is the first study conducted for medical use of an industrial-grade, infrared, noncontact thermometer for temperature screening. Our study may have some bias due to skewed sex distribution and febrile case distribution.


  Conclusion Top


This study demonstrated that the temperature recording by industrial-grade noncontact thermometer has poor reliability with a digital thermometer. The area under the ROC was around 80%. These devices may be improved for its role in medicine either as a screening tool or measurement of temperature. The present study opens a path for future studies as new temperature monitoring devices are still required as the world is facing a pandemic every decade.

Recommendation of this study

The role of IGNCT devices for the screening of individuals to identify cases of febrile illness is limited owing to its poor reliability and unacceptable area under the curve for screening large populations.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

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World Health Organization. Pneumonia of Unknown Cause -” China. World Health Organization; 05 January 2020. Available from: https://www.who.int/csr/don/05-January-2020-pneumonia-of-unknown-cause-china/en/ [Last accessed on 2020 Apr 20].  Back to cited text no. 1
    
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Huang C, Wang Y, Li X, Ren L, Zhao J, Hu Y, et al. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China. Lancet 2020;20:30183e5. pii: S0140-6736.  Back to cited text no. 4
    
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Hsiao SH, Chen TC, Chien HC, Yang CJ, Chen YH. Measurement of body temperature to prevent pandemic COVID-19 in hospitals in Taiwan: Repeated measurement is necessary. J Hosp Infect 2020;105:360-1.  Back to cited text no. 7
    
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    Figures

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