Temperature Isn’t a Good Litmus Test for Coronavirus, Doctors Say

Wall Street Journal – September 21, 2020

Jonathan Hausmann, MD (Rheumatology, BIDMC) discusses temperature monitoring in children, noting that previously undiagnosed children with periodic fever syndrome are surfacing due to parents more closely monitoring changes in temperature during the pandemic.

Teaching assistant Crystal May checked the temperature of kindergarten student Lewis Henry Thompson last month at Newton County Elementary School in Decatur, Miss

Across the country, the litmus test for many children’s entry into school, athletics and extracurricular activities, is their temperature. But experts and medical groups increasingly say that isn’t a good gauge of Covid-19 as many infected children and adults don’t get fevers. Furthermore, variability in individual temperatures as well as questions about the accuracy of body-temperature scanners and infrared contact-free thermometers put such checks at risk of potential error.

In some cases parents are taking their children’s temperatures so often that doctors say they are diagnosing more cases of periodic fever syndrome than usual. Periodic fever syndromes are autoinflammatory disorders in which children have recurrent episodes of fever and other symptoms. Though the genetic conditions are considered rare, doctors say they often go undiagnosed.

In other cases doctors have been stumped by parents who say their otherwise healthy children have had low-grade temperatures for months, unclear if it is connected to an undiagnosed, asymptomatic Covid-19 case or not.

A U.S. Centers of Disease Control and Prevention study of nearly 300 children with Covid-19 found that 56% had a fever. Its current guidance for school reopenings recommends against symptom screening for Covid-19. The American Academy of Pediatrics’ interim guidance on school reopenings similarly doesn’t recommend universal temperature checks.

“Thinking that you have done enough by simply screening a child for a temperature is one of those things that we felt created potentially a false sense of security for schools,” says Nathaniel Beers, a pediatrician at Children’s National Hospital in Washington, who co-chaired the committee that drafted the guidance.

Doctors say baseline temperature varies depending on age, gender and other factors. Temperatures also fluctuate throughout the day based on a person’s circadian rhythm.

Doctors define a normal temperature as 98.6 degrees Fahrenheit and a fever as 100.4 degrees Fahrenheit or higher based on an 1868 study by German researcher Carl Reinhold August Wunderlich. But researchers such as Philip Mackowiak, an emeritus professor of medicine at the University of Maryland School of Medicine, have questioned the research and published studies showing the average human temperature may be slightly lower and vary based on gender, age and time of day. Wunderlich “had a massive database but he didn’t publish his calculations,” Dr. Mackowiak says. “His thermometers calibrated higher than current thermometers. And yet that’s a number we still look to as a definition of the lower limits of the febrile range.”

An adult’s temperature varies by on average one degree Fahrenheit over the course of a day, though for some it can be several degrees, says Dr. Mackowiak who published a 1992 study in JAMA demonstrating this. Similar findings have been published by researchers at Stanford and Harvard.

Dr. Mackowiak’s study found from a population-level standpoint that oral temperatures peak in the evening at 99.9 degrees.

Similarly, a 2018 study in the Journal of General Internal Medicine crowdsourced oral temperatures from 329 participants using a smartphone app and found that average oral temperatues were 97.7 degrees and a fever was defined as 99.5 or higher. Temperatures varied throughout the day and were affected by gender and age.

Most studies have focused on adults, not children, so the normal range of temperature in children remains unknown, says Julie Parsonnet, who specializes in infectious diseases at Stanford University. Dr. Parsonnet was the senior author of a study published this year that found the average adult’s body temperature is about 97.5 degrees.

Every morning Jenny Martin takes her daughter Sloane’s temperature and types the number into a health survey on her phone. Before Sloane enters her second-grade classroom, she is checked again by a teacher using a contactless forehead thermometer.

“We just keep a thermometer right by her toothbrush and it’s part of the daily routine now,” Ms. Martin says. Sloane, who is 8 years old, returned to her private school in Boca Raton, Fla., three weeks ago. “We’re aware that a fever is no longer the first indicator of Covid or the be-all and end-all, but it’s something.”

Dr. Mackowiak says infrared thermometers usually held near the forehead are problematic because they aren’t standardized and their temperature readings can be affected by sweat, makeup on the forehead or even the time of day.

The focus on temperature has led to two perplexing phenomena, say some pediatric rheumatologists in the Northeast. They say they are seeing an uptick in children with recurrent low-grade fevers and those with new diagnoses of periodic fever syndromes.

Jonathan S. Hausmann, a pediatric and adult rheumatologist at Boston Children’s Hospital and Beth Israel Deaconess Medical Center, runs an auto-inflammatory disease clinic that is seeing more patients. He says people are more closely monitoring changes in temperature due to fears of Covid-19, so previously undiagnosed children with periodic fever syndrome are surfacing. Before the pandemic, parents may have attributed fevers to other viral infections. But with children exposed to fewer other people now, parents are noticing periodic fevers more.

“It’s not that these are becoming more frequent,” Dr. Hausmann says. “We’re recognizing them more readily because everyone’s concerned about fevers.”

Beth Gottlieb, head of pediatric rheumatology at Cohen Children’s Medical Center in New Hyde Park, N.Y., says she has observed the same, particularly for PFAPA—Periodic Fever, Aphthous Stomatitis, Pharyngitis, Adenitis—a type of periodic fever syndrome that often affects children under age 5. “We’re seeing a sudden surge of these kids,” Dr. Gottlieb says. “Typically we don’t see a lot of them, maybe once a month. I’ve had six of them in the last month or two.”

For many genetic syndromes, people have an underlying predisposition for the condition but an environmental factor—which could be anything from a virus to stress—may trigger the disease.

Separately Dr. Gottlieb says she has seen more parents coming in with children who have consistent low-grade fevers. If a child is otherwise normal and happy she advises parents to stop taking their temperature. “This may be their normal body temperature based on the rhythm of the day,” she says.

Philip Kahn, an associate professor and pediatric rheumatologist at NYU Langone Medical Center, also has observed a number of otherwise healthy children who have a daily recurrent fever. “Previously I might have seen a kid like this once every three or four years,” he says. He has seen 13 since May. None of the children reported having Covid-19 though they may have had asymptomatic cases. They had negative antibody tests though such checks aren’t always reliable. One possibility is that the elevated temperatures are an aftereffect of Covid-19. Another possibility, says Dr. Kahn, is that the shutdown—which meant more time indoors and less outside—led to changes in some children’s bodies.

Taking Temperatures

While touchless thermometers are handy, the most accurate thermometers are oral ones, experts say, which should be used at home.

Ear thermometers are at greater risk of user error—and wax or other blockages may affect their accuracy, says Nathaniel Beers, a pediatrician at Children’s National Hospital in Washington. Readings from a forehead thermometer that touches the skin can be thrown off by a person’s activity or blood flow to the forehead.

Axillary temperatures, which are taken in the armpit, are generally a degree lower so one degree should be added to the reading. Temperatures taken with a rectal thermometer are slightly higher than oral temperatures but typically used only with infants.

Dr. Beers says thermometers’ accuracy decreases with use and different thermometers have different lifespans. People should regularly check the accuracy of their thermometers and not assume they still work.