Trust Index: Can a pulse oximeter spot COVID-19 early?

People using pulse oximeters, medical devices that measure the saturation of oxygen in red blood cells. (CNN)

JACKSONVILLE, Fla. – We put claims that devices that measure how much oxygen you have in your blood can identify coronavirus disease through our Trust Index.

You probably recognize these pulse oximeters. Nurses often put one on the tip of your finger to check your vital signs at your regular check-up.

Pulse oximeters remain out of stock Monday on the websites of both CVS and Walgreens. Quartz, a news site “for a new generation of business leaders” reported that U.S .sales of pulse oximeters spiked on Jan. 20 when the country’s first COVID-19 case was confirmed and again in mid-February . While the rate of increase slowed, sales have continued to grow each week since, the outlet reported.

The buying frenzy was partially fueled by an op-ed in The New York Times in which emergency room physician Richard Levitan suggested that the devices could provide early warnings about a need for treatment against COVID-19.

The idea behind using one makes sense. Many patients with severe cases of coronavirus disease have had extremely low levels of oxygen in their blood.

But experts with the American Lung Association and the American Thoracic Society said that, for most people, having a pulse oximeter at home won’t really help you spot the virus early. They say low oxygen levels are a relatively late indicator of the coronavirus, so by the time that happens you have likely already had other symptoms like fever, a cough and body aches.

Pulse oximeters used at home can also give you inaccurate readings. Nail polish, acrylic nails and cold hands can all interfere with the light used by the devices and give inaccurate readings.

As for smartphone apps that claim to use the built-in camera as a pulse oximeters, experts say don’t trust them. Your phone’s camera light cannot create the wavelengths needed to get an accurate reading.

After a review of literature and hearing from medical professionals, we urge caution about the use of pulse oximeters for identifying COVID-19 or any other disease. Even though these devices can be useful in the professional setting, the at-home versions can give inaccurate readings.

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