Intended for healthcare professionals

Letters Pulse oximetry and race

Racial bias in pulse oximetry: more statistical detail may help tackle the problem

BMJ 2021; 372 doi: (Published 02 February 2021) Cite this as: BMJ 2021;372:n298
  1. Keir E J Philip, clinical research fellow1,
  2. Robert Tidswell, clinical research fellow2,
  3. Charles McFadyen, clinical research fellow2
  1. 1National Heart and Lung Institute, Imperial College London, Royal Brompton Campus, London SW3 6HP, UK
  2. 2Bloomsbury Institute for Intensive Care Medicine, University College London, Centre for Intensive Care Medicine, Cruciform Building, London, UK
  1. k.philip{at}

We were glad to see a news article1 highlighting research by Sjoding and colleagues2 which identifies a racial bias in pulse oximetry, with hypoxaemia identified less frequently in black people compared with white. The research is valuable, identifying an important matter; however, further details would aid clinical application of the findings.

Useful, additional, commonly used metrics absent from the paper include bias, precision, limits of agreement, and accuracy value. A comparison of these metrics between groups would assist interpretation of the research findings and help identification of potential solutions.

The news article1 rightly highlights controversies regarding “race adjustments” in relation to renal function measurement. Regarding pulse oximetry, some form of adjustment for individual patients’ skin colour maybe appropriate given how it works (transmittance or reflectance of light). Such adjustments could potentially be built into future pulse oximeters; however, a bedside adjustment may be the least bad approach in the immediate short term until a concrete solution is found. Additionally, if the matter could be rectified with a correction based on the patient’s skin colour, there is no obvious reason why oximeters should not be calibrated to darker skin and the bedside adjustment made for readings taken from lighter skin.

Sjoding and colleagues2 also note the relevance of their findings to the covid-19 pandemic. Indeed, we also identified suboptimal accuracy of pulse oximetry in people with covid-19 when looking at those stepping down from intensive care units.3 In these patients, skin colour (67% of our patients were from ethnic minorities) is likely to be one of multiple potential factors that could negatively impact the accuracy of pulse oximetry.

In summary, further statistical detail regarding how the accuracy of pulse oximetry is impacted by skin colour would have been useful in tackling this important matter.


  • Competing interests: None declared.

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