Happy New Year from PEMLit!
Where can I find this paper?
What is this paper about (what is the research question)?
Which method of temperature measurement – axillary, tympanic or temporal artery thermometry – is the best predictor of rectal temperature in febrile and afebrile children?
Summary of the Paper
Design: Prospective single-centre observational (?diagnostic) study
Objective: to determine the most accurate non-invasive method of thermometry
Tests of Interest: Axillary digital thermometer – 5 minutes. Tympanic infrared thermometry as per manufacturer’s instructions (right and left ears). Temporal artery thermometry as per manufacturer’s instructions.
Reference Standard: rectal thermometry – mercury thermometer for 3 minutes.
Primary outcome: test characteristics and correlation coefficients for each method.
Population: Children aged 2-12 years presenting to the Emergency Room of a single centre in Delhi, India.
- Inclusion: Not clear from methods section
- Exclusion: Abnormal ear or rectal anatomy, thermoregulatory disturbances, family history of malignant hyperthermia, diaphoresis, Hb <8g/dL, severe malnutrition/severe wasting (WHO classification), uncooperative, crying, unconscious.
Results: 100 patients were enrolled, 50 “febrile” (Rectal T>38) and 50 “afebrile”.
Temporal artery thermometry had the highest correlation coefficient for both febrile (0.99) and afebrile (0.91) children.
In the detection of fever;
Axillary thermometry had sensitivity 80% and specificity 100% (no confidence intervals given).
Tympanic thermometry had sensitivity 98% and specificity 98% (no confidence intervals given).
Temporal artery thermometry had sensitivity 80% and specificity 98% (no confidence intervals given).
Temporal artery thermometry has the potential to replace rectal thermometry in the busy Emergency Room setting among children aged 2-12 years.
On the study design
Papers like this make me so sad! This could be such a great study – I’ve been asking the question “how should we measure temperature and what do we mean by fever?” for such a long time, and this simple study design has great potential to answer the question. Rectal thermometry is upheld as the “gold standard” in determining temperature but is not without risk.
Unfortunately, there are a few gaps. We don’t know how the patients were selected, so there could be all sort of bias and confounders we don’t know about. And what about excluding children who were crying? OK, it might make them a bit warmer – but who’s been in a Paediatric ED which isn’t filled with crying children?!
That said, they have a good size sample (100 subjects) and seem to have powered the study appropriately. But another question that arises is about the reliability of the measurements, in particular their standard rectal (mercury) thermometry. Who was reading these temperatures? How do we know their assessment is reliable – where is the kappa score?
What were the results and what does this mean?
In terms of correlation with rectal temperature, termporal artery thermometry came closest, with temperatures in 50/50 febrile and 49/50 afebrile children reading within +/- 0.4 degrees of their rectal temperature.
Axillary temperature seemed to correlate better in both groups than tympanic temperature.
Tympanic thermometry had the highest sensitivity for detecting fever (98%), making it the best at ruling fever out, while axillary thermometry was the most specific (100%). No confidence intervals were given. Are these figures useful in clinical practice? No, probably not.
What can we take from this paper into clinical practice?
Despite the suspicious methodology, it certainly seems as though infrared temporal artery thermometry is the closest proxy for rectal thermometry, and with 99% of measurements within +/-0.4 degrees it seems reasonable to suggest it as the preferred method of ED thermometry in those aged 2-12 years.
More questions to ask
- As a gold standard, how reliable is rectal thermometry?
- What is the best method for children under 2 years of age, for whom tympanic thermometry is not considered to be an option?
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