Non-contact infrared thermometers compared with current approaches in primary care for children aged 5 years and under: a method comparison study

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.

Modelling the effects of low indoor temperatures on the lung function of children with asthma

INTRODUCTION

While many epidemiological studies have shown that low outdoor temperatures are associated with increased rates of hospitalisation and mortality (especially for respiratory or cardiovascular disease), very few studies have looked at the association between indoor temperatures and health. Such studies are clearly warranted, as people have greater exposure to the indoor environment than the outdoor environment.

OBJECTIVES

To examine the relationship between various metrics of indoor temperature and lung function in children with asthma. Our specific research questions were: (1) In which room of the home is temperature most strongly associated with lung function? (2) Which exposure metric best describes the relationship between indoor temperature and lung function? (3) Over what lag/time period does indoor air temperature affect lung function most strongly?

METHODS

The Heating Housing and Health Study was a randomised controlled trial that investigated the effect of installing heaters in the homes of children with asthma. This study collected measurements of lung function (daily) and indoor temperature (hourly). Lung function and indoor temperature were measured for 309 children over 12 049 child-days. Statistical models were fitted to identify the best measures and metrics.

RESULTS

The strongest association with lung function was found for the severity of exposure to low bedroom temperatures averaged over the preceding periods of 0-7 to 0-12 days. A 1°C increase in temperature was associated with an average increase of 0.010, 0.008, 10.06, 12.06, in our four measures of lung function (peak expiratory flow rate (PEFR) morning, PEFR evening, forced expiratory volume in 1 s (FEV1) morning and FEV1 evening).

CONCLUSIONS

Indoor temperatures have a small, but significant, association with short-term variations in the lung function of children with asthma.

Role of temperature in determining effects of thyroxine and propylthiouracil on the motor unit

Neuromuscular function and body temperature were measured in five groups of rats: 1) hyperthyroid, 2) thyroidectomized hypothyroid, 3) saline control (euthyroid), 4) propylthiouracil hypothyroid and 5) propylthiouracil control (thyroxine plus propylthiouracil). Significant differences occurred among the five groups in twitch and 30/sec. tensions and percentage tension remaining after 5 seconds of stimulation (but not in tetanic tension); the groups ranking in the order one to five (hyperthyroid lowest). Body temperature differences occurred in the inverse order. Twitch and 30/sec. tension, and tension remaining at 5 seconds showed significant inverse temperature coefficients. When the contribution of temperature differences among groups is removed, only the tension elicited during 30/sec. stimulation is a function of treatment. Propylthiouracil exerts nonthyroidally mediated neuromuscular effects, blocked by curare. It is hypothesized that hyperthyroidism reduces muscle tension by reducing the duration of active state of muscle by a) a direct effect on the mechanism controlling the duration and/or b) an indirect effect on the mechanism by an increase in muscle temperature.

Temperature effects on day old Drosophila pupae

Day old Drosophila pupae were subjected to a variety of closely controlled temperature shocks. Twenty-five hours after puparium formation (at 23°), temperatures from 39.5–41.5° (Q₁ = 2.3) differentially disturb the formation of the posterior crossvein. Three other separate treatments disturb posterior crossvein formation: treatments in the range 36.0–37.0° at 25 hours; 37.3–37.8° at 25 hours; and 39.5–41.5° at 19 hours. Certain qualitative effects are associated with certain temperatures: elliptical holes are seen in wings of flies exposed 25 hours after puparium formation to temperatures from 37.3–37.8°. Anterior crossvein defects ensue if animals are similarly exposed to temperatures from 37.9–38.2°. Within the physiological range, animals raised at higher temperatures are more resistant to the effects of temperatures at 39.5–41.5°. An extremely rapid temperature adaptation by exposures to temperatures in the range 31–38° results in markedly greater resistance to heat shock; here resistance to production of crossvein defects increases faster than to death. The association between qualitative effects and treatment temperatures is modified by changing the temperature at which the animals spend their first day of pupal life. Summation experiments support conclusions drawn from the simpler experiments. Genetic variation and interspecific variation are discussed in the present context, as well as implications of the role of protein denaturation in the biological effects of high temperatures and further, more general experiments.

Temperature and the reproduction of lambda-phage mutants

Groman, Neal B. (University of Washington, Seattle). Temperature and the reproduction of two lambda-phage mutants. J. Bacteriol. 84:438-445. 1962.-A comparative study of phage lambda, and mutants lambdatem and lambda11(2), was made, with particular emphasis on the effect of elevated temperature (44 C) on phage reproduction. Phage lambdatem was selected at 44 C and lambda11(2) was isolated from the late-lysing fraction of bacteria at 37 C. All three phages are similar in their host range, immunity pattern, and in the rate of inactivation of free phage by anti-lambda antibody and heat. Differences were observed in their plaque size and in their relative plating efficiency at 37 and 44 C. One-step growth curve studies showed that phages lambda and lambdatem are similar in the time intracellular phage appears and in their rate of maturation at 37 C. These time and rate parameters were unchanged at 44 C. Both lambda and lambdatem exhibited a reduced latent period at 44 C. However, the latent period of lambdatem was longer than that of lambda at both 37 and 44 C, and its relative 44 C/37 C yield was about 40% while that of lambda is about 3%. Phage lambdatem may be characterized as a lambda mutant with an altered latent period. Phage lambda11(2) was similar to lambda and lambdatem at 37 C, but at 44 C behaved quite differently. The time of appearance of intracellular phage was delayed, compared to 37 C, and the rate of maturation was slower. Phage production at 44 C was about 16% that at 37 C. On further investigation, it was observed that induced Escherichia coli K-12 (lambda11(2)) failed to lyse at 44 C, although it did lyse at 37 C. Lysis inhibition was imposed almost immediately by transferring cells from 37 C to 44 C at any time during the reproductive cycle, including the lytic phase. The behavior of lambda11(2) at 44 C disposed of the possibility that the lytic step was the only step in the phage cycle sensitive to variations in temperature. However, it appeared that the lytic step was a consistant target for its action.

The effect of temperature on the uptake of radiosulfate by rat renal tissue from radiosulfate-containing solutions in vitro

Kidney cortex slices incubated in vitro at 0 degrees C. accumulate radiosulfate from the incubation medium. This process differs from the previously described uptake of radiosulfate by renal tissue incubated at 38 degrees C., for instance, in the lesser sensitivity of the uptake at 0 degrees C. to differential effects of Na(+) as compared with K(+) ions, and of sucrose as compared with glucose. Phlorizin inhibits radiosulfate accumulation at 0 degrees C., whereas it enhances the uptake at 38 degrees C. Effects of the cations K(+) and Na(+) and of phlorizin at temperatures intermediate between 0 degrees and 38 degrees C. have been studied. Parallels have been noted between the accumulative processes for radiosulfate of kidney slices maintained at 0 degrees C. and of mitochondria isolated from rat liver and kidney cortex. These similarities may be attributed to an important role of radiosulfate uptake by mitochondria in slice accumulation of radiosulfate in the cold.

A temperature-gradient bar and its applications to the study of temperature effects on the growth of Reiter's treponeme

Cannefax, George R. (Communicable Disease Center, Atlanta, Ga.). A temperature-gradient bar and its applications to the study of temperature effects on the growth of Reiter's treponeme. J. Bacteriol. 83:708-710. 1962.-A temperature-gradient device is described which employs a constant heat source and an aluminum bar with 294 holes to accommodate small test tubes. Examples of the range and degree of temperature gradients are presented, and the factors affecting heat conduction and heat losses are discussed. Three temperature gradients obtained under different conditions are shown graphically. The usefulness of the temperature-gradient bar in determining the optimal temperature for the cultivation of Reiter's treponeme is presented. The optimal temperature range was found to be 33 to 35 C. The potential usefulness of the temperature-gradient bar in other biological studies is suggested.

Sweating and body temperatures following abrupt changes in environmental temperature

Human subjects were transferred between environments imposing different levels of heat stress. Analyses of measurements obtained after a reasonably steady state had been achieved in each of several environments revealed equally good correlation between a) sweat rate and ear temperature (tympanic membrane), and b) sweat rate and calculated deep skin temperature (hypothetical). The correlations are consistent with adjustment of sweating in response to either hypothalamic temperature or temperature of skin receptors or some combination of the two. However, during the first 20 min after transfer, changes in sweat rate and skin temperature occurred together and in the same direction, but were not accompanied by any consistent change in ear temperature. Thus, to the extent that ear temperature represents hypothalamic temperature, an hypothesis of control of sweating based on hypothalamic temperature alone is not tenable. Alternative physiological explanations are given for data developed elsewhere and used in support of an hypothesis of sweat control solely from the hypothalamus.

Submitted on August 14, 1961