The reliability of a pulse oximeter as an indicator of Covid-19 has been the subject of debate in recent months.

People have become accustomed to having their temperature checked during the pandemic because fever is a key indicator of Covid-19. A new commentary by medical scholars, however, proposes that taking a temperature is a less useful indicator of infection in older adults, and that a pulse oximeter be used instead.

The commentary, by Washington State University College of Nursing Associate Professor Catherine Van Son and Clinical Assistant Professor Deborah Eti, has been published in Frontiers in Medicine.

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Oximeter or not

The reliability of a pulse oximeter as an indicator of Covid-19 has been the subject of debate in recent months. In January, the World Health Organization (WHO) listed the use of the pulse oximeter to identify Covid patients who may need to be hospitalized due to low oxygen levels.

But in February, the US Food and Drug Administration (FDA) warned that pulse oximeters could yield inaccurate results under some circumstances. It said a number of factors — including, poor circulation, skin pigmentation, skin thickness and temperature — can affect the accuracy of the reading.

Also in February, the US Centers for Disease Control and Prevention (CDC) updated its coronavirus guidance to warn healthcare professionals that data from a number of studies suggest skin pigmentation can also affect the accuracy of oximeter readings.

The commentary

The new paper makes a case for preferring an oximeter to a temperature reading in older adults, specifically. It says baseline temperatures are lower in older adults. A lower baseline temperature means a fever may be overlooked using the CDC’s standard definition of 100.4°F or greater, Washington State University said in a press release on the paper.

“In fact, upwards of 30% of older adults with serious infections show mild or no fever,” the paper says.

The authors note that other common signs of Covid, too, may also be dismissed and attributed to ageing, such as fatigue, body aches and loss of taste or smell. Additionally, some Covid-19 patients have no visible signs of having low oxygen levels, such as shortness of breath, yet have oxygen saturation below 90%. Such asymptomatic hypoxia can be associated with extremely poor outcomes.

Van Son and Eti write that inexpensive, portable pulse oximeters should be considered for wide use in Covid-19 screenings of older adults because the devices can detect changes in oxygen saturation without other indications of infection.

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