Characterization of skin tone in Uganda using subjective and objective methods

Summary: Abstract Body: Optical devices (e.g. pulse oximeters) that interact with skin may perform differently depending on skin tone. Regulatory agencies recommend that research and development study cohorts have diverse skin pigmentation. However, definitions for skin pigment have not been adequately validated in global populations and do not fully characterize dark pigmentation, leading to cohorts that may underrepresent people with dark pigmentation. We aimed to characterize the spectrum of skin tone across African populations to ensure representation in common skin pigmentation measurement methods. We conducted a cross-sectional study on healthy adults living in Uganda. The Monk Skin Tone (MST) scale and the Konica Minolta CM-700d spectrophotometer were used (by one operator) to assess pigmentation at the forehead. The CIELAB L*, a*, b* values from the CM-700d were captured in triplicate, and the mean was converted to individual topology angles (ITA). We enrolled 244 participants from 10 African countries. The mean forehead ITA (SD) values for each MST category were: B (4.2°, 13.3), D (-19.0°, 13.7), E (-24.4°, 12.3), F (-41.7°, 8.0), G (-50.1°, 9.2), H (-62.03°, 9.2), I (-68.3°, 6.8), J (-74.2°, 4.6). Approximately 99% of participants had ITA values <10°, 78.9% had mean ITA < -30°, 52.3% had mean ITA < -50°, and 7.2% were <-70°. Currently published ITA cutoffs provide only two categories (< -30 dark° and 10° > ITA > -30° brown) to describe the wide ITA range of 98.8% of study participants. In contrast, four categories exist to describe light skin. Adding additional categories at -10°, -50°, and -70° would provide a more accurate and equitable representation of populations with darker skin tones when using ITA. Brandon Alford¹, Ronald Bisegerwa², Fekir Negussie¹, Michael Lipnick¹, Mary T. Nabukenya^{4, 2}, Elizabeth Igaga^{4, 2}, Tyler Law¹, Danni Chen¹, Leonid Shmuylovich⁵, Jenna Lester¹, Ellis Monk⁶, Ella Behnke¹, Lily Ortiz¹, Fred Bulamba³ 1. University of California San Francisco, San Francisco, CA, United States. 2. Association of Anesthesiologists of Uganda, Kampala, Uganda. 3. Anesthesia, Busitema University, Tororo, Eastern Region, Uganda. 4. Anesthesia, Makerere University College of Health Sciences, Kampala, Central Region, Uganda. 5. Dermatology, Washington University in St Louis, St. Louis, MO, United States. 6. Sociology, Harvard University, Cambridge, MA, United States. Minoritized Populations and Health Disparities Research