PreprintCited by 158Non-Invasive Vital Sign MonitoringHemodynamic Monitoring and TherapyChronic Obstructive Pulmonary Disease (COPD) Research

The DOI matches its Crossref record; 67 of the 68 references it cites were found in a registry or an index, and 1 are not checked yet; 1 of the 38 sources its claims cite were checked for support.

The effects of skin pigmentation on the accuracy of pulse oximetry in measuring oxygen saturation: a systematic review and meta-analysis

Open access

Abstract

Background: Pulse oximetry was widely used in hospitals and at home to monitor blood oxygen during the COVID-19 pandemic. There have been concerns regarding potential bias in pulse oximetry measurements for people with dark skin. We aimed to assess the effects of skin pigmentation on the accuracy of oxygen saturation measurement by pulse oximetry (SpO 2 ) compared with the gold standard SaO 2 measured by CO-oximetry. Methods: We searched Ovid MEDLINE, Ovid Embase, and EBSCO CINAHL Plus (up to December 2021), as well as ClinicalTrials.gov and World Health Organization International Clinical Trials Registry Platform (up to August 2021). We identified studies comparing SpO 2 values in any population, in any care setting, using any type of pulse oximeter, with SaO 2 by standard CO-oximetry; and measuring the impact of skin pigmentation or ethnicity on pulse oximetry accuracy. We performed meta-analyses for mean bias (the primary outcome in this review) and its standard deviations (SDs) across studies included for each subgroup of level of skin pigmentation and ethnicity. We calculated accuracy root-mean-square ( A rms ) and 95% limits of agreement based on pooled mean bias and pooled SDs for each subgroup. Results: We included 32 studies (6505 participants); 27/32 (84.38%) in hospitals and none in people’s homes. Findings of 14/32 studies (43.75%) were judged, via QUADAS-2, at high overall risk of bias. Fifteen studies measured skin pigmentation and 22 referred only to ethnicity. Compared with standard SaO 2 measurement, pulse oximetry probably overestimates oxygen saturation in people with dark skin (pooled mean bias 1.11%; 95% confidence interval 0.29% to 1.93%) and people described as Black/African American (pooled mean bias 1.52%; 0.95% to 2.09%) (moderate- and low-certainty evidence). These results suggest that, for people with dark skin, pulse oximetry may overestimate blood oxygen saturation by around 1% on average compared with SaO 2 . The bias of pulse oximetry measurements for people with other levels of skin pigmentation, or those from the White/Caucasian group is more uncertain. The data do not suggest overestimation in people from other ethnic groups such as those described as Asian, Hispanic, or mixed ethnicity (pooled mean bias 0.31%, 0.09% to 0.54%), but this evidence is low certainty. Whilst the extent of mean bias is small or negligible for all the subgroups of population evaluated, the associated imprecision is unacceptably large (with the pooled SDs > 1%). Nevertheless, when the extents of measurement bias and precision are considered jointly in A rms , pulse oximetry measurements for all the subgroups appear acceptably accurate (with A rms < 4%). Conclusions: Low-certainty evidence suggests that pulse oximetry may overestimate oxygen saturation in people with dark skin and people whose ethnicity is reported as Black/African American, compared with SaO 2 , although the overestimation may be quite small in hospital settings. The clinical importance of any overestimation will depend on the particular clinical circumstance. Pulse oximetry measurements appear accurate but imprecise for all levels of skin pigmentation. The evidence relates to clinician-measured oximetry in health care environments and may not be reflected in home pulse oximetry where other factors may also influence accuracy. Author summary: Why was this study done?: Pulse oximetry was widely used in hospital and at home to measure blood oxygen levels during the COVID-19 pandemic. There was uncertainty as to whether skin pigmentation affects the accuracy of pulse oximetry measurements. What did the researchers do and find?: We assessed, via systematic review, the effects of skin pigmentation on the accuracy of pulse oximetry measurement (SpO 2 ) compared with SaO 2 measured by standard CO-oximetry. In people with dark skin, oxygen saturation measured in hospital by pulse oximetry may be overestimated by an average of 1% compared with gold standard SaO 2 , however, the evidence is of low certainty. The accuracy of pulse oximetry measured compared with standard SaO 2 is quite uncertain for people with light or medium levels of skin pigmentation and for people from ethnic groups other than those described in papers as Black or African American. Pulse oximetry measurements appear to have acceptable overall accuracy (with A rms < 4%) for all subgroups of population evaluated whilst the variation of oximetry readings appear unacceptably wide (with the pooled SDs > 1%). What do these findings mean?: Hospital measured pulse oximetry may overestimate oxygen saturation in people with dark skin compared with SaO 2 by approximately 1%. The implications of this finding in different clinical scenarios will vary but could be clinically important. Impacts are likely to be at the thresholds of being diagnosed as having hypoxaemia where even a small SpO 2 overestimation could lead to clinically important hypoxaemia remaining undetected and untreated. How these findings extrapolate to community and home care settings is unclear.

Verified 2026-10-09 · 1 reference not checked yet

Overview

AI snapshot

Written from the paper’s full text.

TL;DR

This systematic review and meta-analysis found that pulse oximetry probably overestimates oxygen saturation in people with high skin pigmentation and in people described as Black/African American compared with CO-oximetry SaO2. Although mean bias was small and accuracy root-mean-square remained below recommended thresholds, measurement precision was poor across subgroups.

Key findings

  • The review included 32 studies with 6505 participants; 15 studies measured skin pigmentation and 22 referred to ethnicity.
  • Pooled mean bias was 1.11% (95% CI 0.29 to 1.93%) for high skin pigmentation (moderate-certainty evidence) and 1.52% (95% CI 0.95 to 2.09%) for people described as Black/African American (low-certainty evidence), indicating overestimation by pulse oximetry.
  • For medium pigmentation, low pigmentation, Asian/Hispanic/mixed ethnicity, and White/Caucasian groups, evidence was uncertain or did not suggest clinically important systematic overestimation.
  • Pooled SDs were generally >1%, indicating unacceptably large imprecision, but calculated Arms values were <4% for all subgroups, which the authors describe as acceptably accurate when bias and precision are considered jointly.

Methods

  • Systematic review and meta-analysis of methods-comparison studies comparing SpO2 from commercially available pulse oximeters with SaO2 measured by standard CO-oximetry; searches covered Ovid MEDLINE, Ovid Embase, EBSCO CINAHL, ClinicalTrials.gov, and WHO ICTRP up to December 2021.
  • Data were pooled separately for skin pigmentation level and ethnicity using a correlated hierarchical effects model with robust variance estimation; mean bias was the primary outcome, with pooled SDs used to calculate Arms and 95% limits of agreement.
  • Risk of bias was assessed with an adapted QUADAS-2, and certainty of evidence for mean bias was assessed using GRADE.

Limitations

  • The authors state that some included studies reported only significance tests or diagnostic accuracy proportions rather than SpO2–SaO2 data by subgroup, limiting meta-analysis; they also note that race and ethnicity were combined for simplicity, that Fitzpatrick-type skin pigmentation scales are blunt, that device, age, condition, and pigmentation-measurement differences were not analysed, that only English-language peer-reviewed publications were searched, and that no risk-of-bias or GRADE approach was specific to this topic.
  • The paper states that most included studies were hospital-based and had limited information on whether devices were appropriate for home self-monitoring, so findings may not reflect home pulse oximetry by patients or carers.
  • Evident from the text: included studies spanned 1985–2021 and some may have used discontinued devices, and meta-analyses showed substantial between-study heterogeneity (e.g., overall I² values often >90% for several pooled estimates).

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Integrity signals

Registry

Crossref · 10.1101/2022.02.16.22271062

Cites

67 of 68 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Figures

Fig. 1 The study selection flowchart. This flowchart shows the number of records and studies at each stage of the study selection process
Fig. 1 The study selection flowchart. This flowchart shows the number of records and studies at each stage of the study selection processCC BY · PubMed Central
Fig. 2 Risk of bias assessment results. The left section of this figure shows risk of bias judgements for each domain of the QUADAS-2 tool for each study and the right section shows applicability judgements for each concern domain of the QUADAS-2 tool for each study. Please see Additional file 4: Box S3 for all signalling questions used in the QUADAS-2 assessment and further considerations
Fig. 2 Risk of bias assessment results. The left section of this figure shows risk of bias judgements for each domain of the QUADAS-2 tool for each study and the right section shows applicability judgements for each concern domain of the QUADAS-2 tool for each study. Please see Additional file 4: Box S3 for all signalling questions used in the QUADAS-2 assessment and further considerationsCC BY · PubMed Central

Verification

Claims the paper makes

27 Not checked yet · 26 Own result · 20 Own method · 20 Own interpretation · 7 No basis given · 1 Supported

Verify all 37 references — free account

Show all 33 claims

  • It may state two separate claims as one. 43
  • Probably not a substantial claim. 45
68 of 68
  • The paper relies on this without support.

    SaO2 measured by CO-oximetry is the gold standard for blood oxygen saturation.

    “The gold standard measure of blood oxygen saturation levels (SaO2) requires a sample of arterial blood and measurement using CO-oximetry.”
  • The paper relies on this without support.

    Pulse oximetry works by beaming light through skin into the blood and inferring an SpO2 reading from the amount of light absorbed.

    “Pulse oximetry works by beaming light through skin into the blood and inferring an SpO2 reading from the amount of light absorbed.”
  • The authors state this as an assumption.

    Ethnicity categories used in the included studies are valid proxies for levels of skin pigmentation when pooling data on pulse oximetry bias.

    “For simplicity, we chose to use the term of ‘ethnicity’ throughout this review given race and ethnicity are context/country-specific concepts and there is no globally accepted classification approach to distinguishing them [58].”
  • The authors state this as an assumption.

    Scales such as the Fitzpatrick scale used in the included studies provide valid measures of levels of skin pigmentation for assessing pulse oximetry bias.

    “We also acknowledge the limitation of using scales like the Fitzpatrick scale to measure levels of skin pigmentation [59]. Such scales are criticised as being too blunt—an issue that impacts on the findings of this review and should be considered in future research.”
4 of 4

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2 of 2

Citations

Cites

Research works printed but not linked: 2

  1. 2016, An investigation into the bias of pulse oximeters, Respirology, 21, 6
  2. 2021, Accuracy of pulse oximetry (SpO2) with different oximeters. Oxygap study, Intensive Care Medicine Experimental, 9, 51

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Metadata

Authors
Shi, C., Goodall, M., Dumville, J., Hill, J., Norman, G., Hamer, O., Clegg, A., Watkins, C. L., Georgiou, G., Hodkinson, A., Lightbody, C. E., Dark, P., & Cullum, N.
Affiliations
  • Manchester Academic Health Science Centre (GB)
  • University of Liverpool (GB)
  • University of Lancashire (GB)
  • University of Manchester (GB)
Corresponding author
Shi, Chunhu
Venue
BMC Medicine
Publisher
openRxiv
Published
2022-02-17
Volume
20
Issue
1
Pages
267-267
ISSN
1741-7015 (ISSN-L)
OpenAlex
W4291754627
Cited by
158
References
68
Citations by year
2026: 32 · 2025: 46 · 2024: 41 · 2023: 33 · 2022: 6
FWCI
2.81
Type
journal article
Language
en
Open access
Licence
cc-by
Locations
  • BMC Medicine (publishedVersion, cc-by)
  • medRxiv (acceptedVersion, cc-by-nc)
  • PubMed Central (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • Research Explorer (The University of Manchester) (publishedVersion, cc-by)
  • CLOK (University of Central Lancashire) (acceptedVersion)
  • Research Explorer (The University of Manchester) (submittedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • Edge Hill University Research Information Repository (Edge Hill University) (submittedVersion, cc-by)
Funders
  • National Institute for Health and Care Research
  • Department of Health and Social Care
Topics
  • Physical Sciences › Engineering › Biomedical Engineering › Non-Invasive Vital Sign Monitoring
  • Health Sciences › Medicine › Surgery › Hemodynamic Monitoring and Therapy
  • Health Sciences › Medicine › Pulmonary and Respiratory Medicine › Chronic Obstructive Pulmonary Disease (COPD) Research
Keywords
pulse oximetry, oxygen saturation, skin pigmentation, measurement accuracy, co-oximetry, arterial oxygen saturation, SpO2, measurement bias, COVID-19 pandemic
MeSH terms
COVID-19, Oxygen Saturation, Humans, Oximetry, Oxygen, Skin Pigmentation, Pandemics

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