Summary of "Effect of skin tone on the accuracy of the estimation of arterial oxygen saturation by pulse oximetry: a systematic review"

Stimulated significantly by the Covid-19 pandemic’s diagnostic and therapeutic reliance on pulse oximetry, a comprehensive and thoughtful systematic review that “included all relevant studies to date” (but only published in English and mostly from high-income countries) concluded that “pulse oximetry can overestimate true SaO₂ in people with darker skin tones.” 44 studies of widely varying types and methodology were included, covering a total of 222,644 patients who had 733,722 paired measurements of SpO₂ vs. SaO_2. 31% of subjects “were of non-White ethnicity or had non-light skin tones.” The authors stated: “The majority of studies reported overestimation of SaO₂ by pulse oximetry in participants with darker skin tones or from ethnicities assumed to have darker skin tones. Several studies reported no inaccuracy related to skin tone. Meta-analysis of the data was not possible.” The degree of difference could not be specified, but “but its magnitude is likely to be greater when SaO₂ is lower.” No clinical scenarios were offered, but the implication of this bias that may fail to recognize hypoxemia “in patients with darker skin tones and therefore expose these patients to a greater risk of harm” is clear. Interestingly, the authors did not conclude with the usual plea for further and more definitive research.