Pediatric Fever – Myth 1/10: What is a low grade fever?

Myth #1: Oral temperatures between 98.7° and 100° F are low grade fevers.

Fevers! Everyone seems to be afraid of them, but should we be? The short answer is…well, sometimes. What does the evidence tell us? This is part 1 of a 10-part series where I will busting what I consider to be the top 10 myths involving pediatric fever. 

Because of the normal variation in body temperature, there is no single value that universally defines as fever. However, the following are generally accepted values.¹

• Rectal temp > 100.4° F – A rectal temp is considered the most accurate route of measurement
  • Less preferred options include the following:
    • Tympanic membrane > 100.4° F in rectal mode or 99.5° F in oral mode.
    • Temporal artery (or forehead) temp above 100.4° F
    • Oral temp > 100.0° F
    • Axillary temp > 99.0° F

Axillary, ear and forehead temps are easier to obtain than rectal or oral temperatures, BUT, they are much less accurate. So if the thermometer reads close to a fever, its best to confirm them rectally in infants or orally in children who can cooperate and keep their mouth closed around the probe. 

Body temperature tends to be lower in early morning and peaks in the late afternoon into the night. The lowest temps tend to occur around 4 AM and the highest tend to occur around 10 pm. Don’t change practice based on this, but understand it happens. 

Herzog LW, 1993²

• This study published in 1993 in clinical pediatrics set out to define fever in infants < 3 months old. It Involved 691 infants who had rectal electronic temperatures measured at well baby visits. They challenged the universal fever definition of 38.0° C (which is 100.4° F).Investigators took the average temperatures obtained in well appearing children at these routine checkups +/- 2 SD above mean (so > 95th percentile). They found that 6.8%of well infants had measured fevers; fevers were higher in the summer months and that the level at which a true fever was defined increased with age of the infant. 

I scoured all of the literature I could find looking at using peripheral measurement for fever and out of all of these studies I found only 8 unique results to summarize…..^3-18

1. DO NOTuse a peripheral thermometer when temp will influence clinical decision. If you need to know an accurate temp…get a rectal on everyone. 
2. Oral temps are preferred for screening for fever if child is old enough.
3. You cannot accurately convert an axillary temp to rectal temp
4. Ear is more accurate than other options and reasonable for screening well children
5. Ear is better at ruling-in fever
6. A forehead reading of > 37.7 predicts rectal temp of 38.3 in kids 1-4 years of age
7. Rectal temp is still the gold standard 
8. Rectal temp is the onlyscreening method that should be used in infants < 3 mo, even if the child is well appearing. 

Banco, L 1990¹⁹

This publication is quite behind the times, as mercury thermometers are a thing of the past. But it has some historical value, so I have included it here.  

It was a 1990 study published in clinical pediatrics that tested the ability of 200 mothers to read 3 preset thermometers. They were literally handed 3 different thermometers and asked to read the temperature being displayed. Half were in urban hospital based pediatric offices and only 10% of those could read all 3 thermometers. The other half were in suburban private practice based pediatric offices and 93% could read all 3.

Lets summarize the evidence….

• Temperatures between 98.7 and 100 are normal. 
• The body’s normal temperature changes throughout the day. 
• It peaks in the late afternoon and evening and lowest in the early morning just before sunrise. 
• A true low-grade fever is100 to 102° F (37.8° – 39° C).

So, for our first myth questioning if oral temperatures between 98.7° and 100° F are considered low grade fevers….I would consider this BUSTED

Author: Nicholas McManus, DO

References 

1. Fever. nlm.nih.gov/medlineplus/ency/article/003090.htm. Medline Plus website. Accessed March 20, 2019. 
2. Herzog, LW, & Coyne, LJ. (1993). What Is Fever?: Normal Temperature in Infants Less than 3 Months Old. Clinical Pediatrics, 32(3), 142–146. https://doi.org/10.1177/000992289303200303
3. Niven DJ, et al. (2015). Accuracy of peripheral thermometers for estimating temperature: a systematic review and meta-analysis. Ann intern Med, 163(10):768-77. https://doi.org/10.7326/M15-1150
4. Paes BF, et. al. (2010). Accuracy of tympanic and infrared skin thermometers in children. Arch Dis Child., 95(12);974-8 https://doi.org/10.1136/adc.2010.185801
5. Anagnostakis D, et. al. (1993). Rectal-axillary temperature difference in febrile and afebrile infants and children. Clin Pediatr (Phila), 32(5):268-72. https://doi.org/10.1136/bmj.320.7243.1174
6. El-Radhi AS, Patel S. (2006) An evaluation of tympanic thermometry in a paediatric emergency Department.Emerg Med J., 23(1):40-1. doi:10.1136/emj.2004.022764
7. Brennan DE, et al. (1995) Reliability of infrared tympanic thermometry in the detection of rectal fever in children. Ann Emerg Med, (1):21-30. doi: 10.1016/S0196-0644(95)70350-0 ·
8. Nimah MM. (2006). Infrared tympanic thermometry in comparison with other temperature measurement techniques in febrile children. Pediatr Crit Med, 7(1):48-55. doi: 10.1155/2016/1729218
9. Hay AD, et al. (2004). The use of infrared thermometry for the detection of fever. Br J Gen Pract, 54(503):448-50.PMID: 15186568
10. De Curtis M, et al. (2008). Comparison between rectal and infrared skin temperature in the newborn. Arch Dis Child Fetal Neonatal Ed,93(1):F55-7.
11. Titus MO, et al. (2009). Temporal artery thermometry utilization in pediatric emergency care. Clin Pediatr (Phila), 48(2):190-3. https://doi.org/10.1177/0009922808327056
12. Hebbar K, et al. (2005). Comparison of temporal artery thermometer to standard temperature measurements in pediatric intensive care unit patients. Pediatr Crit Care Med, 6(5):557-61.PMID: 16148817
13. Callanan D. (2003). Detecting fever in young infants: reliability of perceived, pacifier, and temporal artery temperatures in infants younger than 3 months of age. Pediatr Emerg Care, 19(4):240-3.
14. Greenes DS, Fleisher GR. (2001). Accuracy of a noninvasive temporal artery thermometer for use in infants. Arch Pediatr Adolesc Med, 155(3):376-81. doi: 10.1136/bmjopen-2015-009509
15. Hoffman RJ, et al. (2013). Comparison of temporal artery thermometry and rectal thermometry in febrile pediatric emergency department patients. Pediatr Emerg Care, 29(3):301-4. doi:10.1097/PEC.0b013e3182850421
16. Teller J, et al. (2014). Accuracy of tympanic and forehead thermometers in private paediatic practice. Acta Paediatr, 103(2):e80-3. doi: 10.1111/apa.12464
17. Teran CG, et al. (2012). Clinical accuracy of a non-contact infrared skin thermometer in paediatric practice. Child Care Health Dev, 38(4);471-6. Doi: 10.1111/j.1365-2214.2011.01264.x
18. Fortuna EL, et al. (2010). Accuracy of non-contact infrared thermometry versus rectal thermometry in young children evaluated in the emergency department for fever. J Emerg Nurs, 36(2):101-4.
19. Banco, L., Jayashekaramurthy, S. (1990). The Ability of Mothers to Read a Thermometer. Clinical Pediatrics, 29(6), 343–345. https://doi.org/10.1177/000992289002900611

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Nicholas McManus

Emergency Physician at Lake Michigan Emergency Specialists - Core faculty member at West Michigan EM Residency - Michigan State University COM Clinical Faculty - Founder of Banana Bag Blog

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