Three types of skin-surface thermometers: a comparison of reliability, validity, and responsiveness

Abstract

Objective: To compare the reliability, validity, and responsiveness of a thermistor thermometer (thermistor) and two different infrared thermometers (one designed to measure tympanic temperature and one for skin temperature).

Design: Reliability and validity were evaluated by making two separate measurements from the skin at identical spots of each hand, forearm, shoulder, thigh, shin, and foot in 17 healthy subjects. Intramuscular temperature was recorded at the hand and shin sites. Test-retest reliability was calculated using intraclass correlation for each instrument. Pearson correlation assessed the relationship between the skin and intramuscular temperatures at the hand and shin sites (validity). Each instrument's ability to measure temperature change (responsiveness) was assessed by measuring skin temperatures serially from 17 limbs of ten patients with complex regional pain syndrome undergoing intravenous regional sympathetic blockade. Responsiveness index values were calculated.

Results: Reliability was strong and similar for each device (intraclass correlation: thermistor = 0.96, tympanic = 0.96, skin = 0.97), as was validity (r: thermistor = 0.90, tympanic = 0.92, skin = 0.92). Responsiveness was marginally better for the infrared skin device (responsiveness index: skin = 4.2, tympanic = 3.6, thermistor = 3.6).

Conclusions: For the purposes of clinical electrodiagnostic laboratory and other physiatry applications, the performance of the infrared thermometers is equal to or superior to that of the traditionally used thermistor. All three devices are highly reliable and valid, whereas the infrared skin device is slightly more responsive. Infrared thermometers have the advantage of being quicker to operate and more portable.