Validation of Commercially Available InfraredThermometers for Measuring Skin SurfaceTemperature Associated with Deep and

Surrounding Wound InfectionAsfandyar Mufti, BMSc; Patricia Coutts, RN;

and R. Gary Sibbald, BSc, MD, MEd, FRCPC(Med)(Derm), MACP, FAAD, MAPWCA, DSc(Hons)

ABSTRACTOBJECTIVE: Increased local skin temperature is a classic sign of

wound infection, repetitive trauma, and deep inflammation.

Noncontact infrared thermometers can help to detect increases in

skin surface temperatures; however, most scientifically tested

devices are far too expensive for everyday wound care providers

to use in routine clinical practice. This noninferiority study was

conducted in an attempt to determine whether 4 less expensive,

commercially available noncontact infrared thermometers have a

similar level of accuracy as the scientifically accepted Exergen

DermaTemp 1001 (Exergen Products, Watertown, Massachusetts).

DESIGN, SETTING, AND PARTICIPANTS: Using an observational

study design, participants with open wounds were randomly

selected from a chronic wound clinic (n = 108). Demographic data

and wound location were documented for all participants. Skin

temperatures were recorded using 5 noncontact infrared

thermometers under consistent environmental conditions. The

thermometer brands were as follows: Exergen DermaTemp,

Mastercool MSC52224-A (Mastercool Inc, Randolph, New Jersey),

ATD Tools 70001 Infrared Thermometer (ATD Tools Inc, Wentzville,

Missouri), Mastercraft Digital Temperature Reader (Mastercraft

Canada, Toronto, Ontario, Canada), and Pro Point Infrared

Thermometer (Princess Auto, Winnipeg, Manitoba, Canada). Data

analysis was based on the skin surface temperature difference

($T in degrees Fahrenheit) between the wound site and an

equivalent contralateral control site.

OUTCOME MEASURES: One-way analysis of variance was used

to compare the mean $T values for all the 5 thermometers,

followed by post hoc analysis. Demographic data were analyzed

using descriptive statistics. Interrater reliability was assessed

for consistency using the intraclass correlation coefficient.

MAIN RESULTS: No statistical difference was reported between

the $T values for the 5 different thermometers (F4,514 = 0.339,

P = .852). Post hoc analysis showed no significant difference when

the thermometers were compared with the Exergen DermaTemp

1001, and Mastercool MSC52224-A (P = .987), ATD Tools 70001

Infrared Thermometer (P = .985), Mastercraft Digital Temperature

Reader (P = .972), and Pro Point Infrared Thermometer (P = .774).

The results for intraclass correlation demonstrated a high

reliability and agreement between raters, as the intraclass correlation

coefficient values for all thermometers were greater than 0.95.

CONCLUSIONS: The results of this study demonstrate that less

expensive, industrial-grade noncontact infrared thermometers

have reliable temperature readings to identify and quantify the

temperature gradients that along with other signs may be

associated with deep and surrounding wound infection or tissue

injury due to repeated microtrauma.

KEYWORDS: infrared thermometers, wound infection, measuring

skin surface temperature

ADV SKIN WOUND CARE 2015;28:11Y6

INTRODUCTION/LITERATURE REVIEWTemperature plays a pivotal role in the body and its outer skin

covering to regulate metabolic and homeostatic processes. The

skin is the largest body organ that also serves as a barrier against

pathogens, contains nerve endings for sensation, acts as storage of

lipids and water, controls evaporation, and is involved in ther-

moregulation. The importance and relationship between body

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Asfandyar Mufti, BMSc, is a Medical Student, University of Ottawa Faculty of Medicine, Ottawa, Ontario, Canada. Patricia Coutts, RN, is Wound Care/Clinical Trials Coordinator, Toronto

Regional Wound Healing Clinic, Mississauga, Ontario. R. Gary Sibbald, BSc, MD, MEd, FRCPC (Med) (Derm), MACP, FAAD, MAPWCA, DSc (Hons), is Professor of Medicine and Public

Health, University of Toronto, Ontario, Canada; Director, International Interprofessional Wound Care Course & Masters of Science in Community Health (Prevention & Wound Care), Dalla

Lana School of Public Health, University of Toronto; Past President, World Union of Wound Healing Societies; Course Coordinator, International Interprofessional Wound Care Course at

New York University Medical Center; Clinical Editor, Advances in Skin & Wound Care, Philadelphia, Pennsylvania. The authors have disclosed they have no financial relationships related to

this article. Submitted August 27, 2014; accepted in revised form November 11, 2014. Editor’s note: For more information on how practitioners can incorporate infrared skin thermometry

for everyday wound care practice and also explore the potential for home use by patients with neuropathy to self-detect damage, see the Clinical Management Extra.

surface temperature and disease have been recognized by phys-

icians for centuries. As early as 400 bc, Hippocrates wrote, ‘‘In

whatever part of the body excess of heat or cold is felt, the disease

is there to be discovered.’’1 Changes in body surface temperature

can be a sign of infection, repetitive trauma, or deep inflammation,

along with less common thromboembolic processes and immune

and metabolic disorders.

Studies conducted by Armstrong et al2Y4 and Lavery et al5Y7

demonstrated the importance of self-monitoring skin temperature

in patients with diabetes, especially those at risk for lower-extremity

complications. These studies demonstrated that regions of elevated

temperature in individuals with diabetic neuropathy were more

likely to ulcerate, unless clinicians introduced aggressive preventive

strategies including plantar pressure redistribution, contact casts

(removable or irremovable), or pneumatic walkers.

More recently, Fierheller and Sibbald8 reported the relationship

between increased periwound skin temperature and local wound

infection in patients with chronic leg ulcers. Prolonged healing of

chronic wounds is a problem that causes tremendous patient dis-

tress and discomfort. Furthermore, delayed wound healing increases

the risk of additional complications and significantly adds to health-

care costs.9,10

Increased periwound temperature is a classic sign of wound in-

fection and is the most reliable clinical sign of deep and surrounding

skin infection, when analyzed with individual factor analysis of

the STONEES (size, temperature,os,new, exudate, erythema and

edema, smell) criteria.11 The quantitative measurement of skin tem-

perature as part of wound assessment facilitates the monitoring of

wound-associated deep and surrounding infection.11 It is impor-

tant to note, however, that an elevated temperature alone does

not necessarily mean that there is an infection. Two or more other

clinical features of the STONEES criteria are also needed that in-

clude increased size, probing or exposed bone, new areas of break-

down, erythema/edema = cellulitis, and increased exudate or smell.

The diagnostic accuracy of manual finger palpation to determine

skin temperature is very limited, especially because it is more sub-

jective than objective.12 Conventional mercury or electronic ther-

mometers are difficult to attach to the wound or periwound skin,

need time to be calibrated, and because of incomplete surface con-

tact are prone to inaccurate readings.13 A handheld nonYskin con-

tact infrared thermometer has the potential to provide an accurate,

objective, and quantitative comparative measurement of skin sur-

face temperature.13

The basic premise behind infrared thermometry is as follows: All

objects above the temperature of absolute zero release infrared

radiation.14 Heat released by inflammation is a form of infrared

radiation. When this infrared radiation hits a sensor in the ther-

mometer, the sensor converts this energy into a specific electrical

signal that corresponds to a given temperature. The higher the

temperature, the greater the infrared radiation received by the sen-

sor that outputs a larger temperature.

Most skin surface infrared thermometers used in everyday clin-

ical practice are of scientific study quality and too expensive for most

healthcare professionals to incorporate into practice. The authors’

goal is to test the accuracy of 4 less expensive commercially avail-

able infrared thermometers normally used for industrial machines

and automobiles. These thermometers will be compared with the

scientifically accepted Exergen DermaTemp 1001 infrared thermo-

meter (Exergen Products, Watertown, Massachusetts) utilized in

several peer-reviewed published studies.2Y7,15Y23

METHODS AND MATERIALSAn observational study design provided both an economic and

simple method for investigation. The Central Ethics Board approval

was obtained, and consenting participants were purposefully re-

cruited from within the patient population of a chronic wound clinic

using specific inclusion/exclusion criteria. One hundred eight patients

(n = 108) with wounds were measured for surface temperature.

Demographic data (eg, age, height, weight, gender, and ethnicity)

were also collected from all patients. Each limb was measured using

5 different devices (Table 1 and Figures 1 and 2).

(1) Exergen DermaTemp 1001;

(2) Mastercraft Digital Temperature Reader (Mastercraft Toronto,

Ontario, Canada);

Table 1.

INFRARED THERMOMETER SPECIFICATIONS

Device Measurement Range Operating RangeAccuracy (AmbientTemperature = 25-C)

Distance-to-Size Ratio

ContinuousScanning

‘‘Maximum’’Temperature

Exergen DermaTemp 1001 18-C to 43-C (65- F to 110- F) 16-CY43-C (60-FY110- F) T0.1-C (0.2- F) 1:1 Yes YesMastercraft DigitalTemperature Reader

j30-C to 480-C (j22-F to 896- F) 0-CY50-C (32- FY122- F) T2.0-C (4.0- F)a 8:1 Yes Yes

ATD Tools 70001Infrared Thermometer

j60-C to 550-C (j76- F to 1022- F) 0-CY50-C (32- FY122- F) T1.5-C (2.7- F) 12:1 Yes Yes

Pro Point InfraredThermometer

j60-C to 500-C (j76-F to 932- F) 0-CY50-C (32- FY122- F) T1.0-C (1.8- F) 12:1 Yes Yes

Mastercool MSC52224-A j58-C to 932-C (j50-F to 500- F) 0-CY40-C (32- FY104- F) T2.0-C (4.0- F) 12:1 Yes Yes

aAccuracy at ambient temperature 23-C.

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(3) ATD Tools 70001 Infrared Thermometer (ATD Tools Inc,

Wentzville, Missouri);

(4) Pro Point Infrared Thermometer (Princess Auto, Winnipeg,

Manitoba, Canada); and

(5) Mastercool MSC52224-A (Mastercool Inc, Randolph,

New Jersey).

The Mastercool MSC52224-A was introduced 2 days late into

the study and was tested on a total of 87 patients (n = 87) over the

course of the study. Under consistent environmental conditions,

skin temperature data were obtained from both the target (wound

site) and contralateral control sites at a distance of 3 cm above

the skin using each of the thermometers for a total of 5 patient

recordings.

In the case of wounds located in the sacral region, the authors

compared the target temperature with an unwounded area above

or below the wound. This was a standard procedure for all wounds

that were anatomically located along the midline and did not have

a ‘‘contralateral’’ side as a comparator.

Temperature readings were made approximately 10 minutes

after removing the wound dressings. This delay was timed to avoid

heat collected under occlusive dressings or evaporation artifacts.

Using gun-shaped infrared thermometers in this study was easy

and intuitive. Once the trigger was depressed, real-time tempera-

ture acquisition started. The authors moved the thermometer over

and around the wound in a ‘‘grid pattern’’ to ensure that all regions

surrounding the wound were covered. The temperature was recorded

in degrees Fahrenheit for convenience of detecting temperature

differentials. The location of the wound and the contralateral site

was also recorded. The target temperature was subtracted from

the contralateral temperature, in order to obtain the temperature

difference/gradient: $T. To validate the interrater reliability of the

thermometer between clinicians, the principal investigator and an

experienced wound care nurse duplicated temperature readings

independently on 20 participants.

Participants were included if they (1) were 18 years or older, (2)

provided written informed consent, (3) participated in 1 study as-

sessment, and (4) had a wound. Participants were excluded if they

(1) were younger than 18 years, (2) were unable to consent due to

language barrier, or (3) had no current skin ulcer.

Data AnalysisStatistical analysis was conducted using SPSS Statistics 22 for

Windows (IBM, Armonk, New York). A 1-way analysis of variance

compared the mean $T between the 5 different thermometers.

Figure 1.

COMMERCIAL LOWER COST INFRARED THERMOMETERS WITH ESTIMATED US DOLLAR COST

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Post hoc analysis was conducted using Tukey test to compare

4 different thermometers, with the DermaTemp Exergen 1001 as

the criterion standard. Interrater reliability of the 5 different thermo-

meters was analyzed using intraclass correlation coefficient. Further-

more, a 2-way mixed model was selected for analysis. The authors

used an > level of .05 as the cut-off point for all test significance.

RESULTSA total of 188 patients (n = 108) participated in the study. The

study population consisted of 61 men (n = 61) and 47 women

(n = 47). All demographic data were reported by the patient. The

mean age ranged from 26 to 94 years (mean, 62.9 [SD, 15.55] years).

The weight ranged from 100 to 480 lb (mean, 194.68 [SD, 66.23] lb).

The reported height ranged from 60 to 80 inches (mean, 67.93 [SD,

4.32] inches). The wound duration varied from 5 days up to 6 years

(mean, 21.49 [SD, 18.2] months). Forty-four percent (n = 47) of the

participants were diagnosed with diabetes at the time of their visit.

Eighty-nine percent (n = 42) of these patients had type 2 diabetes.

The study wounds had a wide variety of etiologies (Figure 3).

A 1-way analysis of variance yielded no significant difference

between the 5 different thermometers in regard to the $T value

(F4,514 = 0.339, P = .852). Post hoc analysis using Tukey honest

significant difference indicated that the DermaTemp thermometer

did not have a significantly different$T value when compared with

Mastercool MSC52224-A (P = .987), ATD Tools 70001 Infrared

Thermometer (P = .985), Mastercraft Digital Temperature Reader

(P=.972), and Pro Point Infrared Thermometer (P= .774). The mean

$T value for each thermometer is indicated in Table 2.

The interrater reliability was examined with the calculation of

the intraclass correlation coefficient. for each thermometer. There

was a high level of consistency and agreement between the 2 clin-

icians and the 5 thermometers (Table 3).

DISCUSSIONThis clinical study was conducted to demonstrate that readily avail-

able infrared thermometers have an acceptable accuracy for clinical

practice. The statistical analysis of periwound temperature data

strongly supports the reliability between thermometers and

Figure 2.

COMPARISON OF INFRARED THERMOMETER SCREENS SHOWING DESIRED MAXIMUM READING, FARENHEIT SCALE

AND SCANNING MODE

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operators of less expensive devices when compared with DermaTemp

Exergen 1001. The strong interrater reliability that was obtained for all

5 thermometers confirms that the less expensive thermometers give

similar temperature readings, regardless of the operator.

The study thermometers had valuable bedside tool features. All

the thermometers had real-time scanning features. Thus, once the

temperature acquisition started, the temperature would change as

the thermometer was moved across a surface instead of pressing

the button each time the operator moved to a new location. Ar-

guably the most important feature in these thermometers is the

‘‘maximum temperature recorded’’ function. During the course of

temperature acquisition, it is difficult for the clinician to remem-

ber the maximum temperature that was observed over and around

the wound. This is because skin surface temperature is variable

Figure 3.

Table 2.

THEMEANTEMPERATUREGRADIENTSOFTHE5 DIFFERENT THERMOMETERS

Thermometer Mean ‘‘$T’’

Exergen DermaTemp 1001 2.39- F (SD, 3.54- F)Mastercool MSC52224-A 2.68- F (SD, 4.06- F)a

ATD Tools 70001 Infrared Thermometer 2.67- F (SD, 3.93- F)b

Mastercraft Digital Temperature Reader 2.72- F (SD, 4.26- F)c

Pro Point Infrared Thermometer 3.01- F (SD, 3.90- F)d

aP = .987.bP = .985.cP = .972.dP = .774.

Table 3.

INTERRATER RELIABILITY ASSESSED USINGINTRACLASSCORRELATIONCOEFFICIENT(ICC)

Thermometer ICCa

Exergen DermaTemp 1001 0.967 (0.92Y0.987)ATD Tools 70001 Infrared Thermometer 0.970 (0.925Y0.988)Pro Point Infrared Thermometer 0.969 (0.922Y0.987)Mastercool MSC52224-A 0.968 (0.92Y0.987)Mastercraft Digital Temperature Reader 0.952 (0.884Y0.981)

a95% Confidence interval values stated in parenthesis.

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over a given surface area and may depend on vascular supply,

inflammation, and infection. The authors’ previous work has

already demonstrated that a temperature difference of greater

than 3-F between a wound and mirror anatomical site, along

with 2 or more other clinical signs, is highly suggestive of deep

infection.8 Individual factor analysis for the clinical signs in the

7 STONEES criteria identified an elevated temperature to be

8 times more likely associated with deep and surrounding infec-

tion. All of the other 6 signs were 2 to 5 times more likely.8 In fact,

the elevated temperature gradient is one of the most important

indications of deep and surrounding infection. Although tempera-

ture elevation is suggestive of deep infection, it is also indicative of

other causes of tissue damage. In the case of tissue damage, it is

important to correct the cause and prevent further tissue damage.

Systemic antibiotics should be ordered only when there is a deep

and surrounding tissue infection.

An important feature of the infrared thermometers in this study

is the distance-to-spot ratio. As the name suggests, this is a ratio

between the distance to the object and the diameter of the object.

For instance, if a device has a distance-to-spot ratio of 8:1, what

this implies is that if the infrared thermometer was 8 inches away

from the wound, the highest temperature within a 1-inch diameter

of the wound surface would be recorded. The closer the thermo-

meter is to the wound, the smaller the diameter of skin tempera-

ture differential that will be recorded. For a smaller wound, better

temperature discrimination occurs in a smaller diameter if the

thermometer is closer to the wound but not touching. The non-

contact infrared thermometers tested in this study may help prevent

the spread of infection. This is because of the higher distance-to-

spot ratio, compared with the Exergen DermaTemp 1001, and

the thermometers did not need to be too close to the wound, avoid-

ing accidental contact and the risk of contaminating other wounds

with subsequent examinations. In the authors’ experience, the

Exergen DermaTemp 1001 examination will cause wound care pro-

viders to accidently touch portions of the wound that could be a

cause of future contamination to other patients. The thermometers

should be swabbed with alcohol or other disinfectants between

examinations.

Some of these thermometers also have a laser pointer. It is a

common misconception that the laser pointer reads the tempera-

ture. It is most important to ensure that the aperture of the infrared

thermometer is pointing at the wound and surrounding surface.

Depending on the model of the infrared thermometer, temperature

will be read above, below, or around the laser pointer. Another

common misconception about infrared thermometers is that they

provide information regarding internal temperature. This is abso-

lutely false. Infrared thermometers are only skin surface tempera-

ture tools.

CONCLUSIONSThe results of this study demonstrate that less expensive, industrial-

grade noncontact infrared thermometers possess reliable temper-

ature readings that identify and quantify temperature gradients in

the periwound skin. This study further demonstrates that infrared

thermometers can add objectivity to the time-honored subjective

method of clinical palpation for elevated skin temperature asso-

ciated with deep and surrounding wound infection.

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