{
  "registry": "KnowYourPrime Evidence Registry",
  "license": {
    "name": "CC BY 4.0",
    "url": "https://creativecommons.org/licenses/by/4.0/",
    "attribution": "Credit KnowYourPrime and link to the finding URL."
  },
  "fields": {
    "devices": "Devices this finding names, including models it says it does not cover. What was actually tested is in scope.applies_to; exclusions are in scope.does_not_cover.",
    "evidence": "Studies by role: anchor (the rating rests on it), conflicting, null_result, supporting.",
    "industry_ties": "Device-maker ties listed in Europe PMC metadata: author_affiliations names makers an author lists as an affiliation, funders names makers listed as funding. stated_ties holds ties a paper states only in its own conflict, funding or acknowledgement text, each read from that statement and worded to say only what it says. Sources are Europe PMC metadata, funding printed in the abstract, and those reviewed statements. An empty list means no tie was found there, not that the study is independent: many papers have no open full text to read. Metadata, not a judgment of the study. checked false means no Europe PMC metadata was available."
  },
  "id": "KYP-ER-0002",
  "version": "1.0",
  "reviewed": "2026-10-24",
  "url": "https://knowyourprime.com/evidence-pulse-oximeter-skin-tone-bias",
  "title": "Pulse Oximeter Accuracy and Skin Tone",
  "question": "Does skin pigmentation change how accurately a pulse oximeter, including one in a wearable, reads blood oxygen?",
  "measurement": "Blood oxygen (SpO2)",
  "devices": [
    "Pulse oximeter",
    "Smartwatch"
  ],
  "rating": {
    "label": "Uncertain",
    "code": "uncertain",
    "definition": "Evidence is conflicting, inconsistent, or difficult to interpret.",
    "rule_version": "1.4",
    "rule_reasons": [
      "Systematic-review or meta-analytic evidence affirms the core relationship.",
      "Multiple supporting studies are consistent with the core relationship.",
      "An anchor study is present but its own reported finding does not cleanly affirm this claim, so it does not count toward the Established threshold.",
      "A clean anchor supports this claim, but an unresolved conflicting study contradicts it on the core relationship, so the evidence is treated as in genuine dispute.",
      "Null-result evidence bears directly on the claimed effect."
    ]
  },
  "conclusion": "The largest and most recent studies find oximeters read blood oxygen higher in people with darker skin, which can hide low oxygen, but several careful studies found no difference and one meta-analysis judged the gap may not be clinically meaningful. The direction is consistent where a difference is found; its size and importance are disputed.",
  "reasoning": [
    "An oximeter that reads high is the dangerous direction, because it can show a reassuring number while arterial oxygen is low. The claim is that this error varies with skin pigmentation.",
    "A meta-analysis of 23 oximetry studies and a large intensive care study with spectrophotometer-measured skin tone both found higher readings for darker skin, and controlled desaturation trials going back to 2005 found the same. Against that, two emergency and intensive care studies with objective or standardized pigmentation measures found no significant difference, and a recent ICU study found no association between skin tone and oximeter error. The rule rates the claim Uncertain because affirming and contradicting evidence both bear on the core question.",
    "Almost all of this evidence comes from finger and clinical oximeters. Wearables use reflected light at the wrist, which has been tested far less."
  ],
  "key_results": [
    {
      "text": "Across 23 oximetry studies (59,684 people, 197,353 paired readings against arterial blood), pooled mean bias was 0.70 percent for light, 0.27 percent for medium and 1.27 percent for dark pigmentation, with accuracy outside the 3 percent regulatory threshold in every group; the authors judged the overestimation may not be clinically relevant.",
      "source": "doi:10.2196/62769",
      "source_url": "https://doi.org/10.2196/62769",
      "source_citation": "Singh et al., Journal of Medical Internet Research, 2024"
    },
    {
      "text": "In 903 critically ill adults and 11,018 paired readings, five fingertip oximeters read 0.6 to 1.5 percentage points higher for darker skin, and readings above 94 percent despite arterial saturation at or below 92 percent were 5.3 to 35.3 percentage points more common with darker skin.",
      "source": "doi:10.1136/bmj-2025-085535",
      "source_url": "https://doi.org/10.1136/bmj-2025-085535",
      "source_citation": "Martin et al., BMJ, 2026"
    },
    {
      "text": "In the same meta-analysis, four wearable pulse-rate studies found no statistically or clinically significant bias by skin pigmentation, so the skin-tone question for wearables is mainly about oxygen, not heart rate.",
      "source": "doi:10.2196/62769",
      "source_url": "https://doi.org/10.2196/62769",
      "source_citation": "Singh et al., Journal of Medical Internet Research, 2024"
    },
    {
      "text": "An intensive care study using colorimeter-measured skin tone found no significant association between skin tone and oximeter error in multivariable analysis.",
      "source": "doi:10.1111/nicc.70433",
      "source_url": "https://doi.org/10.1111/nicc.70433",
      "source_citation": "Barros et al., Nursing in Critical Care, 2026"
    }
  ],
  "scope": {
    "applies_to": "Clinical and fingertip pulse oximeters compared with arterial blood, across skin tone groups, plus wearable pulse-rate accuracy by skin tone.",
    "does_not_cover": "Direct tests of wrist-worn smartwatch blood oxygen across skin tones, which are scarce; any single device brand; medical decisions about oxygen therapy."
  },
  "limitations": [
    "Skin tone was measured in different ways across studies, from color swatches to spectrophotometers, which makes pooled comparisons uneven.",
    "Most evidence is from hospital and laboratory finger oximeters, not consumer wearables.",
    "Several older studies predate current oximeter designs."
  ],
  "evidence": {
    "anchor": [
      {
        "key": "doi:10.1136/bmj-2025-085535",
        "title": "The impact of skin tone on performance of pulse oximeters used by NHS England COVID Oximetry @home scheme: measurement and diagnostic accuracy study.",
        "first_author": "Martin",
        "journal": "BMJ (Clinical research ed.)",
        "year": 2026,
        "url": "https://doi.org/10.1136/bmj-2025-085535",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.1177/10547738251374746",
        "title": "Do Differences in Skin Pigmentation Affect Detection of Hypoxemia by Pulse Oximetry: A Systematic Review of the Literature.",
        "first_author": "Cotton",
        "journal": "Clinical nursing research",
        "year": 2025,
        "url": "https://doi.org/10.1177/10547738251374746",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.2196/62769",
        "title": "Impact of Skin Pigmentation on Pulse Oximetry Blood Oxygenation and Wearable Pulse Rate Accuracy: Systematic Review and Meta-Analysis.",
        "first_author": "Singh",
        "journal": "Journal of medical Internet research",
        "year": 2024,
        "url": "https://doi.org/10.2196/62769",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [
            "Verily Life Sciences"
          ],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.1213/ane.0000000000006755",
        "title": "Low Perfusion and Missed Diagnosis of Hypoxemia by Pulse Oximetry in Darkly Pigmented Skin: A Prospective Study.",
        "first_author": "Gudelunas",
        "journal": "Anesthesia and analgesia",
        "year": 2024,
        "url": "https://doi.org/10.1213/ANE.0000000000006755",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.1097/00000542-200504000-00004",
        "title": "Effects of skin pigmentation on pulse oximeter accuracy at low saturation.",
        "first_author": "Bickler",
        "journal": "Anesthesiology",
        "year": 2005,
        "url": "https://doi.org/10.1097/00000542-200504000-00004",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.1111/j.1553-2712.1998.tb02772.x",
        "title": "Effect of skin pigmentation on pulse oximetry accuracy in the emergency department.",
        "first_author": "Adler",
        "journal": "Academic emergency medicine : official journal of the Society for Academic Emergency Medicine",
        "year": 1998,
        "url": "https://doi.org/10.1111/j.1553-2712.1998.tb02772.x",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "pmid:8914569",
        "title": "Accuracy of pulse oximetry in pigmented patients.",
        "first_author": "Bothma",
        "journal": "South African medical journal = Suid-Afrikaanse tydskrif vir geneeskunde",
        "year": 1997,
        "url": "https://pubmed.ncbi.nlm.nih.gov/8914569/",
        "industry_ties": {
          "checked": false
        }
      }
    ],
    "conflicting": [
      {
        "key": "doi:10.1111/nicc.70433",
        "title": "Accuracy and Bias of Pulse Oximetry in the Intensive Care Unit: A Prospective Observational Study.",
        "first_author": "Barros",
        "journal": "Nursing in critical care",
        "year": 2026,
        "url": "https://doi.org/10.1111/nicc.70433",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      }
    ],
    "null_result": [
      {
        "key": "doi:10.3390/s24113301",
        "title": "Effect of Skin Pigmentation and Finger Choice on Accuracy of Oxygen Saturation Measurement in an IoT-Based Pulse Oximeter.",
        "first_author": "Haxha",
        "journal": "Sensors (Basel, Switzerland)",
        "year": 2024,
        "url": "https://doi.org/10.3390/s24113301",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      }
    ],
    "supporting": [
      {
        "key": "doi:10.1117/1.jbo.31.7.070501",
        "title": "Broad-linewidth sources result in a skin-tone bias in noninvasive optical measurement of oxygen saturation.",
        "first_author": "Blaney",
        "journal": "Journal of biomedical optics",
        "year": 2026,
        "url": "https://doi.org/10.1117/1.JBO.31.7.070501",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.1542/hpeds.2025-008471",
        "title": "Pilot Study: Using Reflectance as a Proxy for Skin Pigmentation to Assess Pulse Oximeter Accuracy.",
        "first_author": "Branstad",
        "journal": "Hospital pediatrics",
        "year": 2026,
        "url": "https://doi.org/10.1542/hpeds.2025-008471",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.3390/s25020559",
        "title": "Monte Carlo Simulation of the Effect of Melanin Concentration on Light-Tissue Interactions in Reflectance Pulse Oximetry.",
        "first_author": "Al-Halawani",
        "journal": "Sensors (Basel, Switzerland)",
        "year": 2025,
        "url": "https://doi.org/10.3390/s25020559",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.1007/s11517-024-03091-2",
        "title": "Pulse oximeter bench tests under different simulated skin tones.",
        "first_author": "Swamy",
        "journal": "Medical & biological engineering & computing",
        "year": 2025,
        "url": "https://doi.org/10.1007/s11517-024-03091-2",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.1016/j.rceng.2024.04.005",
        "title": "Determining factors of pulse oximetry accuracy: a literature review.",
        "first_author": "León-Valladares",
        "journal": "Revista clinica espanola",
        "year": 2024,
        "url": "https://doi.org/10.1016/j.rceng.2024.04.005",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.1117/1.jbo.29.s3.s33311",
        "title": "Dual-ratio approach to pulse oximetry and the effect of skin tone.",
        "first_author": "Blaney",
        "journal": "Journal of biomedical optics",
        "year": 2024,
        "url": "https://doi.org/10.1117/1.JBO.29.S3.S33311",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.1117/1.jbo.29.s3.s33308",
        "title": "Exploring the bias: how skin color influences oxygen saturation readings via Monte Carlo simulations.",
        "first_author": "Narayana Swamy",
        "journal": "Journal of biomedical optics",
        "year": 2024,
        "url": "https://doi.org/10.1117/1.JBO.29.S3.S33308",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.1117/1.jbo.29.s3.s33305",
        "title": "Monte Carlo simulation of the effect of melanin concentration on light-tissue interactions for transmittance pulse oximetry measurement.",
        "first_author": "Al-Halawani",
        "journal": "Journal of biomedical optics",
        "year": 2024,
        "url": "https://doi.org/10.1117/1.JBO.29.S3.S33305",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.4187/respcare.12023",
        "title": "Pulse Oximetry: 2023 Year in Review.",
        "first_author": "Hess",
        "journal": "Respiratory care",
        "year": 2024,
        "url": "https://doi.org/10.4187/respcare.12023",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.4187/respcare.09795",
        "title": "Pulse Oximeter Performance, Racial Inequity, and the Work Ahead.",
        "first_author": "Okunlola",
        "journal": "Respiratory care",
        "year": 2022,
        "url": "https://doi.org/10.4187/respcare.09795",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.4187/respcare.09769",
        "title": "Racial Disparities in Occult Hypoxemia and Clinically Based Mitigation Strategies to Apply in Advance of Technological Advancements.",
        "first_author": "Chesley",
        "journal": "Respiratory care",
        "year": 2022,
        "url": "https://doi.org/10.4187/respcare.09769",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.1513/annalsats.202203-270cme",
        "title": "Racial Disparity in Oxygen Saturation Measurements by Pulse Oximetry: Evidence and Implications.",
        "first_author": "Jamali",
        "journal": "Annals of the American Thoracic Society",
        "year": 2022,
        "url": "https://doi.org/10.1513/AnnalsATS.202203-270CME",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.1097/aln.0000000000004153",
        "title": "Self-reported Race/Ethnicity and Intraoperative Occult Hypoxemia: A Retrospective Cohort Study.",
        "first_author": "Burnett",
        "journal": "Anesthesiology",
        "year": 2022,
        "url": "https://doi.org/10.1097/ALN.0000000000004153",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      },
      {
        "key": "doi:10.1111/j.1365-2044.1991.tb09410.x",
        "title": "Potential errors in pulse oximetry. I. Pulse oximeter evaluation.",
        "first_author": "Ralston",
        "journal": "Anaesthesia",
        "year": 1991,
        "url": "https://doi.org/10.1111/j.1365-2044.1991.tb09410.x",
        "industry_ties": {
          "checked": true,
          "author_affiliations": [],
          "funders": [],
          "stated_ties": []
        }
      }
    ]
  },
  "evidence_last_evaluated": "Oct 25, 2026",
  "rating_history": [
    {
      "date": "2026-07-21",
      "rating": "Uncertain",
      "from": null,
      "rule_version": "1.4"
    }
  ],
  "versions": [
    {
      "version": "1.0",
      "date": "2026-10-24",
      "rating": "Uncertain",
      "change": "First published."
    }
  ],
  "research_desk": "https://knowyourprime.com/research-desk-spo2#skin_pigmentation_bias",
  "related_findings": [
    "https://knowyourprime.com/evidence-wearable-blood-oxygen-accuracy"
  ],
  "related_articles": [
    "https://knowyourprime.com/does-your-wearables-blood-oxygen-reading-work-the-same-for-everyone",
    "https://knowyourprime.com/how-accurate-is-apple-watchs-blood-oxygen-reading"
  ],
  "methodology": "https://knowyourprime.com/methodology",
  "citation": "KnowYourPrime Evidence Registry, Finding KYP-ER-0002, version 1.0, reviewed 2026-10-24. https://knowyourprime.com/evidence-pulse-oximeter-skin-tone-bias"
}