FDA has published a safety communication about the accuracy of pulse oximeters in people with dark skin pigmentation, following a recent call from U.S. senators for the agency to review the accuracy of the devices due to concerns about potential racial disparity in pulse oximeter measurements.
Use of pulse oximeters, which are available as prescription and over-the-counter products, has increased as people have sought out ways to monitor their respiratory status at home in light of the threat posed by the coronavirus pandemic. The trend has intensified concerns about the long-analyzed relationship between skin pigmentation and oximeter results.
FDA responded to the concerns by informing patients and healthcare providers of the limitations of the devices. The agency is encouraging people to track changes in their oxygen levels over time and to factor in evidence other than oximeter data when making decisions.
Interest in pulse oximeters surged early in the COVID-19 pandemic. The devices shine light beams on the fingertip to estimate oxygen saturation in the blood. Consumers sought out the devices to gain a way to assess the effect of the coronavirus on their respiratory systems at home and, in doing so, gain a data point to inform decisions about when to seek medical care. The potential value of the data was increased by the discovery that some people with low oxygen levels display little breathlessness.
Some pulse oximeters are sold OTC as general wellness, sporting or aviation products. OTC oximeters are not intended for medical use and do not undergo FDA review. Other pulse oximeters are cleared via the 510(k) pathway and are available with prescription. Consumers monitoring their own oxygen levels will typically have an OTC oximeter.
Concerns about the effect of skin pigmentation on the accuracy of pulse oximeters date back to at least the 1980s. In the 1990s, researchers published studies of patients in emergency departments and critical care that found no link between skin pigmentation and pulse oximeter results. Yet, earlier and later studies generated conflicting data.
The topic was brought back into the spotlight by COVID-19 and a recent letter in the New England Journal of Medicine. The NEJM letter reported an analysis that found "Black patients had nearly three times the frequency of occult hypoxemia that was not detected by pulse oximetry as White patients." Senators including Elizabeth Warren (D-Mass.) cited the NEJM data in a letter last month asking FDA to review the link between skin pigmentation and pulse oximeter results.
In Friday's safety communication, FDA said it is evaluating the literature on pulse oximeter accuracy, with a "focus on literature that evaluates whether products may be less accurate in individuals with darker skin pigmentation." FDA is also analyzing premarket data and working with manufacturers to assess other evidence. The process could lead to revised guidance on the topic. Existing guidance advises the inclusion of at least two darkly pigmented participants in clinical trials of pulse oximeters.
For now, FDA has limited its actions to a statement about the proper use of pulse oximeters. The FDA safety communication describes how to take and interpret readings. In general, pulse oximeters are less accurate at low blood oxygen levels. FDA said a 90% reading could reflect a real figure of as low as 86% and as high as 94%. The accuracy range of OTC pulse oximeters, which do not undergo FDA review, could be wider still.
Tens of companies compete for the prescription pulse oximeter market. In recent years, multiple Chinese companies have received 510(k) clearances to join other medtechs such as Masimo and Smiths Medical in the market.