Skin Pigmentation Assessment

CIELAB values are used to calculate the Individual Topography Angle (ITA), the FDA-recommended objective skin pigmentation metric as of 2025. 2024 FDA guidance recommends direct skin pigmentation measurement when evaluating pulse oximeters, whose accuracy may vary by skin tone. Two trained research staff members independently assess skin pigmentation at the bedside with input from the patient. The standardized skin pigmentation protocol requires natural sunlight, scanning the midpoint of the inner forearm, and a visual quality check with repeat scanning if results appear discrepant. Pulse oximeter accuracy may vary by skin tone, which motivates direct pigmentation measurement in the trial. Skin pigmentation measured by the Monk Skin Tone Scale (categorized as light, medium, or dark) is a prespecified subgroup for heterogeneity-of-treatment-effect analysis.