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Regulatory Focus™ > News Articles > 2021 > 2 > FDA: Oximeters may be inaccurate in Black patients

FDA: Oximeters may be inaccurate in Black patients

Posted 19 February 2021 | By Kari Oakes 

FDA: Oximeters may be inaccurate in Black patients

The US Food and Drug Administration (FDA) has issued a new safety communication about the limitations of using pulse oximeters to assess blood oxygen levels. The communication is based in part on findings that oximeters may yield falsely elevated readings in individuals with dark skin pigmentation, with the potential of masking dangerously low blood oxygen levels.
The agency’s communication comes in the context of the COVID-19 pandemic, which “has caused an increase in the use of pulse oximeters,” both for home use and in healthcare settings. FDA noted that “although pulse oximetry is useful for estimating blood oxygen levels, pulse oximeters have limitations and a risk of inaccuracy under certain circumstances that should be considered.”
At the end of January, Senators Elizabeth Warren, Cory Booker and Ron Wyden wrote to acting FDA commissioner Janet Woodcock, MD, urging the agency "to quickly conduct a review of the accuracy of pulse oximeters...across racially diverse patients and consumers." 
“Simply put, pulse oximeters appear likely to provide misleading measures of blood oxygen level to patients of color—indicating that patients are healthier than they actually are and increasing their risk of negative health impacts from diseases like COVID-19,” wrote the senators. They submitted a list of questions to Woodcock asking whether FDA has collected data on accuracy of cleared oximeters in various patient subpopulations and whether FDA is monitoring over-the-counter pulse oximetry devices, among other queries.
In addition to providing a range of recommendations for patients and healthcare providers, FDA’s Friday afternoon communication also reiterated that premarket submissions for prescription-use oximeters should have clinical study populations that “are demographically representative of the US population.” Studies, according to FDA guidance, should include at least two darkly pigmented participants, or ensure that 15% of the applicant pool has dark skin pigmentation. In the January letter to Woodcock, Warren and her fellow senators questioned where FDA derived these recommendations, and asked when the guidance was last reviewed.
Although poor circulation, tobacco use, fingernail polish and skin thickness can all interfere with accurate pulse oximetry, it was a recent journal publication about the modality’s potentially dangerous inaccuracy in Black patients that was cited in FDA’s safety communication.
The 17 December 2019 correspondence in the New England Journal of Medicine reports on a study of adult inpatients who required supplemental oxygen at the University of Michigan Hospital, together with intensive care unit patients in 178 other hospitals.
In all, first author Michael Sjoding, MD, and his collaborators at the University of Michigan Medical School examined over 38,000 pairs of oxygen saturation measures from over 8,000 White patients and over 1,300 Black patients. For each patient, there was at least one measure of oxygen saturation by pulse oximetry that was obtained in close temporal relationship to an arterial blood gas measurement.
The investigators found that among Black patients who had an oxygen saturation of 92-96% on pulse oximetry, about 12% had arterial oxygen saturations of less than 88% -- a clinically significant difference and a threshold for clinical concern given the steepness of the oxygen-hemoglobin dissociation curve at that level of oxygenation.  The number of White patients who had this discrepancy between normal pulse oximetry readings and sub-88% arterial oxygenation was much smaller – 3.6%.
“Thus, in two large cohorts, Black patients had nearly three times the frequency of occult hypoxemia that was not detected by pulse oximetry as White patients,” wrote Sjoding and his collaborators. “Our results suggest that reliance on pulse oximetry to triage patients and adjust supplemental oxygen levels may place Black patients at increased risk for hypoxemia… [T]he variation in risk according to race necessitates the integration of pulse oximetry with other clinical and patient-reported data.”
The patient and caregiver recommendations provided by FDA in this updated safety communication include a recommendation to “pay attention to other signs or symptoms of low oxygen levels.” However, the first item on the bulleted list of signs and symptoms is “Bluish coloring in the face, lips, or nails;” darker skin pigmentation can also render invisible any changes in skin tone caused by reduced blood oxygenation. FDA does include other symptoms to monitor, such as shortness of breath and chest pain.
For health care providers, FDA recommends becoming familiar with the accuracy of pulse oximeter brands used in clinical settings. “Pulse oximeters are least accurate when oxygen saturations are less than 80%,” notes FDA, and a given reading should also be interpreted as an estimate, not a measurement with point accuracy.
Pointing to the retrospective data collected by Sjoding and his colleagues, FDA agreed that “Black patients had nearly three times the frequency of occult hypoxemia (low oxygen levels in the blood) as detected by blood gas measurements but not detected by pulse oximetry, when compared to White patients.”


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