Pulse Oximeters Are Less Accurate Among Black, Hispanic and Asian Covid-19 Patients

Pulse oximeter measurements among Black, Hispanic and Asian Covid-19 patients were less accurate than measurements for white patients, a study showed, underscoring shortcomings in a critical device used to monitor the disease’s riskiest outcomes. The discrepancies may have led to some patients of color with severe disease receiving delayed or no treatment despite having oxygen levels low enough to warrant it, researchers said Tuesday in a study published in the journal JAMA Internal Medicine.

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Pulse oximeters are electronic devices that estimate a person’s blood oxygen saturation and pulse rate. The devices, which are used widely in clinical settings and can also be purchased over the counter, are a primary tool for detecting severe Covid-19 because low oxygen levels can be a sign of serious illness. Pulse oximeters, typically clipped on a fingertip, work by shining two lights—one infrared and one red—through the finger and analyzing the results. Several factors have been linked to inaccurate pulse oximeter readings including dark nail polish and poor circulation.

The color of a person’s skin also has been associated with measurement errors. The skin pigment melanin is a possible cause of these potential inconsistencies, said A. Ian Wong, a critical care and lung doctor at Duke University who wasn’t involved in the recent study. Melanin absorbs light and can impact the device’s analysis, Dr. Wong said. The devices tend to overestimate oxygen levels when more melanin is present, research has shown; in other words, in patients with darker skin.

The recent study looked at more than 7,000 patients diagnosed with Covid-19 between March 2020 and November 2021 at five hospitals in the Johns Hopkins Health System. Pulse oximeter measurements were taken for all 7,000 patients. More-accurate but invasive arterial blood gas measurements also were taken from about 1,200 of the patients. When the researchers compared measurements from the arterial blood gas tests with pulse oximeter readings, they found discrepancies among patients of all races but a more pronounced difference for patients of color. Compared with white patients, pulse oximeters overestimated oxygen saturation by an average of 1.2 percentage points among Black patients, 1.1 percentage points among Hispanic patients and 1.7 percentage points among Asian patients.

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The researchers attempted to quantify the impact that biases in pulse oximeter measurements had on treatment outcomes. With statistical models, they used data from the 1,200 patients who received arterial blood gas tests to infer oxygen-saturation levels in the rest of the study population... They concluded that Black patients were almost 30% less likely than white patients to be recognized as being eligible for treatment for severe Covid-19, despite having oxygen levels below the threshold at which such treatment would be recommended. Hispanic patients were more than 20% less likely than white patients to have their treatment eligibility recognized. No significant difference was found for Asian patients.

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