http://doi.org/ 10.33698/NRF0148 –  Rinzin Dolkar, Surinder Kapoor, Neena Vir Singh, Vikas Suri

Abstract: Temperature is one of the most common and important clinical signs. Temperature must be measured accurately to identify fluctuations fast and intervene early. Newer methods have evolved with the hope of replacing the mercury thermometers.There are concerns about the environmental hazards of mercury and the breakages. There have been growing concerns about the potential for mercury poisoning.The present study was conducted to find out the accuracy of the digital thermometer when compared with the clinical mercury thermometer.The study was conducted in the male and female surgical and medical wards of Nehru hospital,PGIMER, Chandigarh. A total of 200 patients were studied, 600 readings each were taken with both the clinical mercury thermometer and the digital thermometers. Using the Bland Altman analysis,it was concluded that the difference between the temperature readings of the two thermometers was not clinically significant .Both the instruments can be used simultaneously. It is recommended that digital thermometers should be used in place of the clinical mercury thermometers as it is environmentally friendly.

Key Words

Accuracy, Clinical Mercury Thermometer, Digital Thermometer, Temperature, Temperature gradient, Preferences

 

Correspondence at:

Rinzin Dolkar

Rapgay Hospital,

Opp. LIC Building, Dakpathar Road Vikasnagar, Dehradun, Uttrakhand – 248198

Introduction

Temperature is one of the most common and impor tant clinical signs. Measurement of a patient’s temperature is a crucial piece of clinical data.Temperature must be measured accurately to identify fluctuations fast and intervene early .1 In the context of other data it can guide diagnostic and therapeutic measures by determining the presence of illness and the extent to which the patient is responding to treatment.z Temperature must be measured accurately to identify fluctuations fast and intervene early.3Accurate monitoring of body temperature is an impor tant nursing procedure.The body temperature is the difference between the heat produced by the body processes and the amount of heat lost to the environment.1The hypothalamus controls the temperature.1The anterior hypothalamus controls heat loss, and the posterior hypothalamus controls heat production.

The ‘gold standard’ for ambulatory patient’s temperature recording has been the mercury in glass thermometers.4Newer methods have evolved with the hope of replacing the mercury thermometers. Extensive review of literature has revealed a lot of facts on why we should stop using the mercury thermometers.Breakages are a constant problem and there are concerns about the environmental hazards of mercury.There have been growing concerns about the potential for mercury poisoning.5 Mercury-in-glass thermometers have been implicated in episodes of cross-infection and outbreaks of diarrhoea caused by salmonella and Clostridium difficile6 Fadzil M. et al7 in 2008 conducted a study on the accuracy of the various non-invasive thermometers iedigital, forehead strip, tympanic and mercury thermometers. He found that the digital thermometer gave the best concordance. Imaniet al8 compared the two body temperature measurements by the mercury and digital thermometers and found no statistical significant difference between the measurements by the two thermometers.

In most of the hospitals in India, including the tertiary care hospitals where the researcher was studying clinical mercury thermometers are still being used. Therefore the researcher felt the need to undertake this study.

Objective

To compare the temperature recordings by the clinical mercury thermometer and digital thermometer.

Materials and Methods

The study was conducted in the male and female surgical and medical wards of Nehru hospital of Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh. The study population consisted of all adult patients admitted in the male and female surgical and medical wards. Purposive and convenient sampling technique was used.Out of a total of 250 patients in the 4 wards, only 200 patients were selected due to the exclusion criteria.(the patientswho were immunocompromised, those who were sleeping and and those who were not present on their beds). The tools were developed after review of literature and consultation with the exper ts in the nursing and medicine depar tments. The tools included: Demographic proforma, temperature protocols for the clinical mercury thermometer and digital thermometer and observation proforma. The instruments used were the standardized Hicks Akutemclinical mercury thermometer manufactured as per standards of ISI 3055(part 1). The digital thermometer was model MT-101 marketed by Ranbaxy laboratories .

Data collection was done after seeking approval from the Ethics Review committee of PGIMER, Chandigarh.

The period of data collection was from 17th July to 31st August 2011.Written consent was taken from the patient /relative before including him /her in the study.The demographic proforma was filled before star ting the procedure.The axillary temperatures were taken simultaneously first using the clinical mercury thermometer under one axilla and then the digital thermometer in the other axilla according to the temperature recording protocols.The temperature readings were noted by the two thermometers . A total of 3 observations each with the two thermometers at 30 minute intervals were taken for each patient .This resulted in a total of 600 observations with the clinical mercury thermometer and 600 observations with the digital thermometer .

The data was entered and analyzed using spss (version 16) and medcalc. The data was presented in percentages, mean, and standard deviation . To assess the concordance between the clinical mercury thermometer and the digital thermometer readings, the Bland Altman test was used. The data was also analyzed using simple linear regression analysis to determine the correlation of temperature gradients at different ranges of temperature .

Results

Out of a total of 200 subjects,45(22.5%) were from the male surgical ward; 54(27%) from the female surgical ward; 58(29%) from the male medical ward; and 43(21.5%) from the female medical ward.The subjects were in the age range of 18 to 87 years with the mean age of 42.08yrs±16.15 SD.

In this study 3 readings each with both the clinical mercury thermometer and digital thermometer were taken for each patient. The procedure was carried out for 200 subjects. This resulted in 600 mercury temperature readings and 600 digital temperature readings. The mean temperature of the mercury thermometer was 98.920 °F±1.6 2SD and the mean temperature recorded by the digital thermometer was 98.86 °F ±1.6 2SD with a range of 94.5 of to 104.5 of for both the temperature readings.

Table 1: Descriptive statistics of the temperature readings (°f) by the clinical mercury and digital thermometers

Mean±SD     RangeThermometers Observations Temperature in °F

 

Mercury                 600      98.92±1.62 95.4-104.5

Digital                   600      98.86±1.62 95.4-104.5

 

Table 2 shows the mean difference in temperature taken by the clinical mercury and digital thermometers. The maximum difference between the mercury and digital readings was 0.3 °F and the minimum difference was 0.10 °F. The mean difference was 0.05 °F ± 0.07SD.

There was no difference in the temperature for 386(64.3%) readings. For 127(21.2%) readings there was 0.1 °F difference in the temperature . There was 0.2

°F difference for 85(14.2%) readings and only 2(0.3 %)readings had 0.3 °F difference in temperature readings by the two thermometer.

Table 2 : Differenceof temperature(°F) in the readings of the clinical mercury and digital thermometers     (N=600)

Temperature in °f                 Difference n (%)Difference in                      Frequency of

 

No difference                        386 (64.3)

0.1                                            127 (21.2)

0.2                                            85 (14.2)

0.3                                            2 (0.3)

Mean difference                     0.05° f ±0.07 SD

Bland Atman Analysis

In order to determine the concordance between the clinical mercury thermometer and the digital thermometer, the Bland Altman method of analysis was used.

Fig 1 depicts the Bland Altman plot of the mercury temperature readings and the digital temperature readings. On the X- axis the mean of the mercury and the digital temperature are plotted and on Y- axis the difference between the temperature readings mercury and digital thermometer are plotted. In this plot a line of mean bias and the lines of 95% limits of agreements are present. Bias is the average of difference between the temperature by mercury thermometer and the digital thermometer. The majority of the readings were falling within the lines of limits of agreement i.e. ±1.96 SD. Only 2 readings were falling outside ±1.96 SD.

Table 3 depicts the summary of the Bland Altman analysis. Here the bias between the mercury and the digital readings was 0.05 °F ±1.96 SD. The upper limit of agreement was 0.20 °F and the lower limit of agreement was – 0.10 °F .

Fig. 1: Bland Altman plot of the mercury and digital temperatures of the subjects

Table 3: Summary of the results of the Bland Altman plot    N=600

Bias (difference       Upper Limit        Lower Limit between temperature of agreement    of agreement by mercury and digital

0.05°f                      0.20°f                  -0.10°f

Regression analysis:To determine the correlation of temperature gradients at different temperatures, simple linear regression analysis was calculated between the difference in the temperature by mercury and digital thermometer (also known as bias) and the increase in temperature.

Fig 2 shows that there was a positive correlation between the difference in temperature between the clinical mercury and digital thermometers (also known as bias) and the increase in temperature but the difference was not statistically significant (r=0.071,r2=0.005, p=0.084.

Fig. 2 : Regression line and scatter plot of the difference in temperature between the clinical mercury and digital thermometers and increase in temperature

Discussion

Temperature is one of the most common and important clinical sign. The gold standard for ambulatory patient temperature recording has been done by the clinical mercury thermometer. Due concerns about the breakages and environmental hazards newer thermometers have evolved with the hope of replacing the clinical mercury thermometer. The present study was conducted to find the concordance of the digital thermometer with the clinical mercury thermometer.

The present study was conducted in the male and female surgical and medical wards of Nehru hospital, PGIMER Chandigarh. A total of 200 subjects participated in the study. The study was conducted by taking the axilary temperatures of the subjects simultaneously with the clinical mercury thermometer and the digital thermometer. Three readings each were recorded for every patient which made a total of 600 mercury temperature readings and 600 digital temperature readings.

The mean temperature by mercury thermometer was 98.92 of±1.62SD and the mean temperature by digital thermometer was 98.86of±1.62SD. The range for both the thermometers was 95.4-104.5°F. In the present study, using the Bland Altman analysis , the mean bias was 0.05°F. The upper and lower limits of agreement were 0.20°F and -0.10°F. A similar study was conducted by Fadzil et al7. The mean bias between the temperature recorded by mercury thermometer and the digital thermometer was 0.049°C and the upper and lower limits of agreement were 0.48°C and -0.59°C. In both the studies the difference is not clinically significant . This variation in temperature is not likely to change any clinical decision.

In a similar study conducted by Chand MS,9 the findings revealed that the mean difference tempreature of reading between the electronic sensor thermometer and the mercury in glass thermometer was 0.10 ± 0.20°C. She stated that the little change in variation by this temperature is unlikely to change any clinical decision .

In the present study the digital thermometer under recorded the tempreature to the extent of 0.1°F to 0.3°F. This is in comparison to a study conducted by Dowding D,10. Her study revealed that the two digital thermometers under recorded the temperature as compared to the mercury thermometer to the extent of 0.278 °C and – 0.348 °C respectively .This was both clinically and statistically significant. It should also be noted that a one way analysis of variance found an influence on the accuracy dependent on which data collector was using the thermometer.

In the present study there was no significant difference between the difference of temperature in mercury and digital thermometer readings (bias) and increasing temperature as per the results of the regression analysis revealed (p=0.084).This is in comparison to a study by Devrin et al11 to measure the accuracy of fever by two tympanic thermometers and axillary temperature using the clinical mercury thermometer.Using the Bland Altman analysis, the limits of agreement were wide i.e. 0.98 and -1.27°C ; and 0.27°C and -1.75°C as compared to 0.20 °F and -0.10 °F in the present study.There was no significant difference in recording with both the thermometers and the variance was there in both higher and lower readings.This is in comparison to the present study where variance was not statistically significant at both higher and lower temperatures. (p=0.084) She recommended that the tympanic thermometer should just be used as a tool for screening and not as a tool for follow up.

The results of the present study show that the digital thermometer is a good alternative to the traditional clinical mercury thermometer.It was concluded from the results of the present study that the difference in the temperature readings between the clinical mercury thermometer and the digital thermometer is of no clinical significance.The digital thermometer should be used as it is environmentally friendly.

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