Impact of Skin Pigmentation on Pulse Oximetry SpO2 and Wearable Pulse Rate Accuracy: A Meta-Analysis (Preprint)

BACKGROUND Photoplethysmography (PPG) is a technology routinely used in clinical practice to assess blood oxygenation (SpO2) and pulse rate (PR). Skin pigmentation may influence accuracy, leading to health outcomes disparities. OBJECTIVE This meta-analysis primarily aimed to evaluate the accuracy of PPG-derived SpO2 and PR by skin pigmentation. Secondarily, we aimed to evaluate statistical biases and the clinical relevance of PPG-derived SpO2 and PR according to skin pigmentation. METHODS We identified 23 pulse oximetry studies (N=59,684; 197,353 paired SpO2-arterial blood observations) and 4 wearable PR studies (N=176; 140,771 paired photoplethysmography-electrocardiography observations). We evaluated accuracy according to skin pigmentation group by comparing SpO2 accuracy root-mean-square (Arms) values to the regulatory threshold of 3% and PR 95% limits of agreement (LoA) values to ±5 bpm, according to the standards of the American National Standards Institute, Advancing Safety in Medical Technology, and the International Electrotechnical Commission. We evaluated biases and clinical relevance using mean bias and 95% confidence intervals (CI). RESULTS For SpO2, Arms were 3.96%, 4.71%, and 4.15% and pooled mean biases were 0.70% (95% CI: 0.17 to 1.22), 0.27% (95% CI: -0.64 to 1.19), and 1.27% (95% CI: 0.58 to 1.95) for light, medium, and dark pigmentation, respectively. For PR, 95% LoAs were -16.02 to 13.54, -18.62 to 16.84, and -33.69 to 32.54 and pooled mean biases were -1.24 bpm (95% CI: -5.31-2.83), -0.89 bpm (95% CI: -3.70-1.93), and -0.57 bpm (95% CI: -9.44-8.29) for light, medium, and dark pigmentation, respectively. CONCLUSIONS SpO2 and PR measurements may be inaccurate across all skin pigmentation groups, breaching FDA guidance and industry standards thresholds. Pulse oximeters significantly overestimate SpO2 for both light and dark skin pigmentation, but this overestimation may not be clinically relevant. PRs obtained from wearables exhibit no statistically or clinically significant bias based on skin pigmentation.