Episode 26 - Characterizing skin pigment in research cohorts

In this episode of BJD Talks, Sam and Meera discuss the article ‘Comparison of methods for characterizing skin pigment diversity in research cohorts’ by Lipnick et al. The full article can be accessed at https://doi.org/10.1093/bjd/ljaf397 

*This podcast was generated by an AI tool created by 67Bricks for the British Association of Dermatologists* 

Transcript

SPEAKER_00 0:00

Welcome to BJD Talks, the official podcast of the BJD. I'm Sam.

SPEAKER_01 0:04

And I'm Mira. In this episode, we will be discussing the article by Michael Lipnick et al. Comparison of Methods for Characterising Skin Pigment Diversity in Research Cohorts, published in October 2025 and included in the January 2026 issue.

SPEAKER_00 0:21

This study addresses a pressing issue, the inequities in how pulse oximeters perform in people with darker skin tones. Devices that function poorly in diverse populations directly contribute to health disparities.

SPEAKER_01 0:34

Precisely. The article highlights how a lack of standardized definitions for skin pigmentation in research cohorts has allowed these devices to be approved despite their inequities. Historically, terms like lightly pigmented or darkly pigmented have been vague and inconsistent.

SPEAKER_00 0:53

The study sought to improve this by comparing both subjective and objective methods for characterizing skin pigment. It tested three subjective scales, the perceived Fitzpatrick, Von Lucian, and Monk Skin Tone scales, alongside objective tools like the Conica Minolta CM700D spectrophotometer and the Delphin Skin Colour Catch.

SPEAKER_01 1:14

What stood out was the inconsistency between methods. For instance, using ITA thresholds, 13.6% of one cohort was classified as having dark skin, but that jumped to 26% using the perceived Fitzpatrick scale. The same group yielded very different results depending on the method used.

SPEAKER_00 1:35

Indeed, the Monk Skin Tone Scale, or MST, showed promise. It provided a wider range of standardized colours and better differentiation, especially for darker skin tones, compared to the Fitzpatrick and Von Lucien scales. Meanwhile, the ITA proved robust as an objective measure, correlating well with spectrophotometric data.

SPEAKER_01 1:57

That said, the study found that the existing ITA threshold for dark skin, ITA less than negative 30 degrees, was too narrow to represent real-world diversity. The authors suggest updated ITA categories to better capture global skin pigment variation.

SPEAKER_00 2:14

Crucially, the authors also recommend avoiding race as a stand-in for skin pigmentation. Their findings show pigmentation varies greatly within self-reported racial categories such as black or African American, further discrediting race as a reliable proxy.

SPEAKER_01 2:30

Exactly. They also propose using both objective and subjective methods in tandem. Scales like the MST can facilitate communication, while measures like ITA provide objective data. This dual approach could mitigate operator bias and enhance accuracy.

SPEAKER_00 2:46

Another significant aspect was anatomical site variation. Pigmentation differed between areas like the forehead, inner arm, and fingertips. The forehead, often correlated with pulse oximeter sites, emerged as a reliable location for assessing pigments. By contrast, fingernail readings were less consistent.

SPEAKER_01 3:06

Of course, the study has limitations. The cohort was predominantly lightly pigmented and relied on pre-existing data, which may not capture the full diversity of skin tones worldwide. Even so, it's a vital step towards addressing inequities in medical research and device development.

SPEAKER_00 3:24

Ultimately, this study has practical implications, particularly for regulatory frameworks, such as those from the FDA or ISO. Ensuring devices account for pigmentation diversity would lead to more equitable healthcare outcomes.

SPEAKER_01 3:38

And that concludes today's episode. Equitable research is not just an ideal, it's essential. Many thanks to Michael Lipnick and his team for shedding light on such an important issue.