Proper use of noncontact infrared thermometry for temperature screening during COVID-19
Authors: Hussain Amber S. , Hussain Heather S. , Betcher Nathan , Behm Robert , Cagir Burt 
Published: June 2021

Among the myriad of challenges healthcare institutions face in dealing with coronavirus disease 2019 (COVID–19), screening for the detection of febrile persons entering facilities remains problematic, particularly when paired with CDC and WHO spatial distancing guidance. Aggressive source control measures during the outbreak of COVID-19 has led to re-purposed use of noncontact infrared thermometry (NCIT) for temperature screening. This study was commissioned to establish the efficacy of this technology for temperature screening by healthcare facilities. We conducted a prospective, observational, single-center study in a level II trauma center at the onset of the COVID-19 outbreak to assess (i) method agreement between NCIT and temporal artery reference temperature, (ii) diagnostic accuracy of NCIT in detecting referent temperature $$\ge 100.0\,^{\circ }{\mathrm{F}}$$

≥
100.0

∘

F

and ensuing test sensitivity and specificity and (iii) technical limitations of this technology. Of 51 healthy, non-febrile, healthcare workers surveyed, the mean temporal artery temperature was $$98.4\,^{\circ }{\mathrm{F}}$$

98.4

∘

F

($$95\%$$

95
%

confidence interval (CI) = $$[98.2,98.6]\,^{\circ }{\mathrm{F}}$$

[
98.2
,
98.6
]

∘

F

). Mean NCIT temperatures measured from $${1}\,{\mathrm{ft}}$$

1

ft

, $${3}\,{\mathrm{ft}}$$

3

ft

, and $${6}\,{\mathrm{ft}}$$

6

ft

distances were $$92.2\,^{\circ }{\mathrm{F}}$$

92.2

∘

F

$$(95\%\ {\text {CI}}=[91.8\ 92.67]\,^{\circ }{\mathrm{F}})$$

(
95
%

CI
=

[
91.8

92.67
]

∘

F
)

, $$91.3\,^{\circ }{\mathrm{F}}$$

91.3

∘

F

$$(95\%\ {\text {CI}}=[90.8\ 91.8]\,^{\circ }{\mathrm{F}})$$

(
95
%

CI
=

[
90.8

91.8
]

∘

F
)

, and $$89.6\,^{\circ }{\mathrm{F}}$$

89.6

∘

F

$$(95\%\ {\text {CI}}=[89.2 \ 90.1]\,^{\circ }{\mathrm{F}})$$

(
95
%

CI
=

[
89.2

90.1
]

∘

F
)

, respectively. From statistical analysis, the only method in sufficient agreement with the reference standard was NCIT at $${1}\,{\mathrm{ft}}$$

1

ft

. This demonstrated that the device offset (mean temperature difference) between these methods was $$-6.15\,^{\circ }{\mathrm{F}}$$

-
6.15

∘

F

($$95\%\ {\text {CI}}=[-6.56,-5.74]\,^{\circ }{\mathrm{F}}$$

95
%

CI
=

[
-
6.56
,
-
5.74
]

∘

F

) with 95% of measurement differences within $$-8.99\,^{\circ }{\mathrm{F}}$$

-
8.99

∘

F

($$95\%\ {\text {CI}}=[-9.69,-8.29]\,^{\circ }{\mathrm{F}}$$

95
%

CI
=

[
-
9.69
,
-
8.29
]

∘

F

) and $$-3.31\,^{\circ }{\mathrm{F}}$$

-
3.31

∘

F

($$95\%\ {\text {CI}}= [-4.00,-2.61]\,^{\circ }{\mathrm{F}}$$

95
%

CI
=

[
-
4.00
,
-
2.61
]

∘

F

). By setting the NCIT screening threshold to $$93.5\,^{\circ }{\mathrm{F}}$$

93.5

∘

F

at $${1}\,{\mathrm{ft}}$$

1

ft

, we achieve diagnostic accuracy with $$70.9\%$$

70.9
%

test sensitivity and specificity for temperature detection $$\ge 100.0\,^{\circ }{\mathrm{F}}$$

≥
100.0

∘

F

by reference standard. In comparison, reducing this screening criterion to the lower limit of the device-specific offset, such as $$91.1\,^{\circ }{\mathrm{F}}$$

91.1

∘

F

, produces a highly sensitive screening test at $$98.2\%$$

98.2
%

, which may be favorable in high-risk pandemic disease. For future consideration, an infrared device with a higher distance-to-spot size ratio approaching 50:1 would theoretically produce similar results at $${6}\,{\mathrm{ft}}$$

6

ft

, in accordance with CDC and WHO spatial distancing guidelines.