Sanidhya Singh

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 systematic review and 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 PPG-electrocardiography observations). We evaluated accuracy according to skin pigmentation group by comparing SpO2 accuracy root-mean-square values to the regulatory threshold of 3% and PR 95% limits of agreement values to +5 or –5 beats per minute (bpm), according to the standards of the American National Standards Institute, Association for the Advancement of Medical Instrumentation, and the International Electrotechnical Commission. We evaluated biases and clinical relevance using mean bias and 95% CI. Results: For SpO2, accuracy root-mean-square values were 3.96%, 4.71%, and 4.15%, and pooled mean biases were 0.70% (95% CI 0.17%-1.22%), 0.27% (95% CI –0.64% to 1.19%), and 1.27% (95% CI 0.58%-1.95%) for light, medium, and dark pigmentation, respectively. For PR, 95% limits of agreement values were from –16.02 to 13.54, from –18.62 to 16.84, and from –33.69 to 32.54, and pooled mean biases were –1.24 (95% CI –5.31 to 2.83) bpm, –0.89 (95% CI –3.70 to 1.93) bpm, and –0.57 (95% CI –9.44 to 8.29) bpm for light, medium, and dark pigmentation, respectively. Conclusions: SpO2 and PR measurements may be inaccurate across all skin pigmentation groups, breaching U.S. Food and Drug Administration guidance and industry standard 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.

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 systematic review and 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 PPG-electrocardiography observations). We evaluated accuracy according to skin pigmentation group by comparing SpO2 accuracy root-mean-square values to the regulatory threshold of 3% and PR 95% limits of agreement values to +5 or –5 beats per minute (bpm), according to the standards of the American National Standards Institute, Association for the Advancement of Medical Instrumentation, and the International Electrotechnical Commission. We evaluated biases and clinical relevance using mean bias and 95% CI. RESULTS For SpO2, accuracy root-mean-square values were 3.96%, 4.71%, and 4.15%, and pooled mean biases were 0.70% (95% CI 0.17%-1.22%), 0.27% (95% CI –0.64% to 1.19%), and 1.27% (95% CI 0.58%-1.95%) for light, medium, and dark pigmentation, respectively. For PR, 95% limits of agreement values were from –16.02 to 13.54, from –18.62 to 16.84, and from –33.69 to 32.54, and pooled mean biases were –1.24 (95% CI –5.31 to 2.83) bpm, –0.89 (95% CI –3.70 to 1.93) bpm, and –0.57 (95% CI –9.44 to 8.29) bpm for light, medium, and dark pigmentation, respectively. CONCLUSIONS SpO2 and PR measurements may be inaccurate across all skin pigmentation groups, breaching U.S. Food and Drug Administration guidance and industry standard 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.

Background: Medicine has used photoplethysmography (PPG) with pulse oximetry devices for decades to assess blood oxygenation (SpO₂) and pulse rate (PR) and this technology is now being used in consumer devices. Skin pigmentation may influence accuracy, leading to health outcomes disparities. Methods: This meta-analysis identified 23 pulse oximetry studies with 59,684 participants and 197,353 paired observations between SpO₂ and arterial blood and 4 wearable PR studies with 176 participants and 140,771 paired observations between PR and electrocardiography. The primary objectives were to evaluate SpO₂ and PR accuracy by skin pigmentation group by comparing SpO₂ accuracy root-mean-square (A_rms) values to regulatory thresholds of 3% and PR 95% Limits of Agreement (LoA) to American National Standards Institute (ANSI), Advancing Safety in Medical Technology (AAMI), and International Electrotechnical Commision (IEC) Standards of ±5bpm. The secondary objectives were to evaluate biases and clinical relevance using mean bias and 95% confidence intervals (CI). Findings: For SpO₂, A_rms was 3·96%, 4·71%, and 4·15% and the pooled mean bias was 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, the 95% LoA were -16.02 to 13.54, -18.62 to 16·84, and -33.69 to 32.54 and the pooled mean bias was -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. Interpretation: The current meta-analysis suggests overall inaccurate SpO₂ and PR measurements across all skin pigmentation groups as they exceed FDA guidance and ANSI standard thresholds. Pulse oximeters also exhibit statistically significant overestimation of SpO₂ for light and dark skin pigmentation, but no clinically relevant bias. Wearable PR exhibits no statistically significant or clinically relevant bias.