INTRODUCTION

Temperature measurement is an important tool not only in arriving at the correct diagnosis but also to start early treatment of a specific condition in febrile infants¹.  Accurate temperature measurement is difficult because of their non-cooperative nature which is further made difficult by the time consuming nature of axillary thermometry. Furthermore, frequent disturbance of the infants may lead to hypoxia and deterioration in their clinical condition, hence minimal handling is fundamental .Thus, a novel technique is the need of the hour while being convenient for infants and at the same time, preserving clinical accuracy of measurement². Measurement of temperature in infants can be obtained by rectal, axillary, and tympanic thermometry. The gold standard is the mercury-in -glass thermometer. However, in practice, every available method has several advantages and disadvantages. The forehead is an excellent area to measure temperature as it is supplied by temporal artery, which receives high blood flow from the carotid artery³. Non-contact infrared thermometer (NCIT) could represent a valid alternative, incorporating quick and non-invasive method, not requiring sterilisation because of no body contact. These reasons make it a candidate for screening of febrile infants^4,5. However, some authors found discordant results on the performance of NCITs ^{3, 6, 7}. Our study was focussed on demonstrating the correlation and agreement of temperature measurement between NCIT with digital thermometer.

METHODOLOGY

This study was an analytical cross-sectional study conducted in the Department of Paediatrics in a tertiary health care facility for a period of two months. Approval from institute research and ethics committee was obtained before commencement of the study. Two hundred and fifty febrile infants(less than 1 year of age) attending Paediatrics OPD were enrolled for the study after obtaining consent from their parents. Sick looking and unstable infants were excluded. EQUINOX EQ-IF-02 was used for non-contact infrared thermometry and Gen-X digital thermometer was used for axillary digital thermometry.  Axillary temperature was taken after wiping underarm with dry towel and digital thermometer probe tip placed under the arm sequentially so the tip remained in contact with skin and temperature recording was recorded after the beep sound from the digital thermometer. Forehead temperature was taken with infrared thermometer at approximately 0.5-1 cm distance from glabella [6]. All temperatures were taken by trained nurse and duty doctor. In every infant, all the measurements were recorded within 6 mins. Age and sex of the infant were recorded and entered into a database. Informed consent for the study was obtained from the parent/guardian.

RESULTS

Data entry was done in MS Excel 2010. SPSS 18.0 software was used to analyse the results.  A difference of 0.5º C was considered clinically acceptable [6, 7]. Among the 250 infants enrolled for the study, 2.4% were under a month old, 97.6% were aged from one month to one year (Table 1). The mean temperature recordings of the two devices were 37.62°C (SD 1.02) and 37.61°C (SD 0.95) respectively. The mean difference between two measurements was found to be -0.036 (95% CI: -0.42 to 0.30).There was a significant correlation between the measurements by NCIT and Digital thermometers (r=0.52; P<0.001). There was significant agreement of measurements (kappa=0.452) by both instruments in measuring the body temperature by NCIT and Digital thermometers. Bland Altman graph was used to depict the results of the study (Figure 1)

Table 1: Descriptive statistics of mean temperature by Age group and type of thermometer (n=250)

Figure 1: Bland Altman Plot for NCIT and Digital Thermometer readings:

DISCUSSION

Many studies confirmed the clinical accuracy of Non-contact infrared thermometry ^8-16. Apa H et al study showed a significant positive correlation between axillary and non-contact infrared thermometer with a correlation coefficient of 0.78 and NCIT showed sensitivity of 71.7% and specificity of 95.8% ⁸. A 2018 study revealed that forehead is the preferred site for temperature measurement by infrared thermometer and that correlation between NCIT forehead and DAT axilla was r = 0.32(-0.38 to -0.25) which is deemed significant[3], concordant with the results of our study.

Though many studies have proven the clinical accuracy of NCIT in clinical settings, some conflicting reports also emerged. A study by Franconi et al comparing DAT and NCIT demonstrated higher temperature measurements of axilla compared to forehead with mean difference of 0.41 degree Celsius ⁶. Another study showed unsatisfactory correlation between axillary digital thermometer and forehead non-contact thermometer with a mean difference in temperature of -0.5 degree Celsius (95%limits of agreement) ⁷. Both these studies show that there is significant disagreement between the temperature measurements of digital and Non-contact infrared thermometer, which is discordant with the results of this study.

CONCLUSION

Moderate agreement and significant correlation of NCIT with Digital thermometry was proven. Thus,Non-contact infrared thermometer has a very good clinical accuracy compared to digital thermometer and thus can be used in paediatric population for measurement of body temperature. Non-contact thermometers offer easier temperature measurements in infants and non-cooperative children and are also safer to use. The results of other studies are controversial and future studies with a larger sample size in Indian infants are needed to prove the accuracy of non-contact thermometer.

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