Hidden Hypoxemia: The Diagnostic Bias Affecting Patient Care


Where access to healthcare is limited, the impact of diagnostic bias based on skin tone can result in a greater burden of disease and even more deaths, especially for Black individuals.

Hidden Hypoxemia: The Diagnostic Bias Affecting Patient Care

Keyaria Gray, DO

Recent studies have shown that pulse oximetry underestimates hypoxemia in individuals with darker skin tones, a term known as hidden hypoxemia. This bias is concerning because it could result in missed diagnoses and inadequate treatment, particularly in patients with underlying respiratory conditions, according to Keyaria Gray, DO, Department of Pediatrics, Duke University School of Medicine, and investigators.

A study based on electronic health records (EHR) that compared the results from arterial blood oxygen saturation (SaO2), which is considered the criterion standard for measuring oxygen saturation levels, with pulse oximetry (SpO2), specifically looked at how pulse oximetry readings compared between Black or African American children and White children.

The study found that pulse oximetry overestimated the oxygen saturation levels more often in Black children than in White children, which is consistent with other studies. All arterial blood oxygen saturation samples were obtained within 1 minute of an SpO2 reading during a pediatric cardiac catheterization, and the accuracy was compared among Black and White infants.

The editorial article stated that by acknowledging such bias embedded within a ubiquitous technology has important implications and raises questions about how to incorporate this knowledge into clinical practice. It also spotlights the impact of algorithmic inaccuracies for certain populations on clinical management and outcomes.

The Implications of Diagnostic Bias

In patient care, vital signs and data points are already the subject of scrutiny for their accuracy from the perspective of healthcare professionals. By raising awareness of these biases and carefully considering them in patient care, clinicians can provide more accurate and effective treatment, ultimately improving patient outcomes, investigators wrote.

As an example, it's understood that a pulse oximetry reading may be falsely normal or high in a patient with carbon monoxide poisoning or in someone suffering with a sickle cell anemia crisis. Information regarding biases of skin in pulse oximetry might be used to interpret the accuracy of the reading.

As a known limitation, the inclusion of this knowledge in the overall consideration of a child’s clinical condition raises important questions:

  • Is the reading accurate in this patient with darker pigmentation or might the true reading be lower?
  • Could this be hidden hypoxemia?
  • Would the reading be more accurate on an area of lighter pigmentation on the patient?

Careful review of these questions could lead clinicians to treat hypoxemia more aggressively in certain populations based on known diagnostic bias, according to the article.

Bias Implications: Low-Middle-Income Countries

The implications of diagnostic bias are different in low to middle-income countries. Pneumonia is the leading cause of death of children younger than 5 years in Sub-Saharan Africa, of which an estimated 31% have hypoxemia.

Health care workers in these regions rely almost exclusively on clinical signs to detect hypoxemia and to guide therapy for a child presenting with generalized pneumonia symptoms.

International aid organizations, governments, and private foundations have invested significant resources in expanding oxygen systems in low and middle-income countried, particularly during the COVID-19 pandemic.

These efforts included donations of pulse oximeters and deploying training modules to primary and secondary health care facilities. Although the provision of these devices was an important step forward, it is critical to recognize the limitations of pulse oximetry in detecting hypoxemia accurately in individuals with darker skin tones.

Without taking this limitation into account, the use of pulse oximetry in these areas could lead to missed diagnoses and inadequate treatment for those who need it most.

Investigators stressed that the implications of this bias are far-reaching, affecting patient care in both high-income and low-income countries. In high-income countries, a missed diagnosis or inadequate treatment resulting from hidden hypoxemia could lead to prolonged hospitalization or even death.

Alternatively, in low-income countries, where access to healthcare and resources is limited, the impact of diagnostic bias can be even more dire. In these settings, missed diagnoses and inadequate treatment can result in a greater burden of disease and even more deaths.

It’s imperative to address and mitigate diagnostic bias in all settings to ensure that patients receive the appropriate care they need, investigators wrote. This includes ongoing research and development of more accurate diagnostic tools and systems, as well as increasing awareness and education among healthcare providers about the limitations of current technologies.


  1. Gray KD, Subramaniam HL, Huang ES. Effects of Racial Bias in Pulse Oximetry on Children and How to Address Algorithmic Bias in Clinical Medicine. JAMA Pediatr. Published online March 20, 2023. doi:10.1001/jamapediatrics.2023.0077
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