The authors reviewed data collected between October 2015 and July 2021, which included 7,183 paired samples (3,201 black and 3,982 white) collected from 75 subjects (39 black and 36 white), who were screened with the same criteria to remove potential bias based on health conditions. All subjects were exposed to the same hypoxia protocol, which varied the arterial saturation of hemoglobin (SaO2) between 70% and 100%. Noninvasive oxygen saturation (SpO2) values were obtained from Masimo SET® pulse oximeters with RD SET sensors and time-matched (within 5 seconds, rather than up to 10 minutes as in the letter to the editor) with arterial blood gas (ABG) samples analyzed using an ABL-835 blood gas analyzer.
The authors analyzed the data to determine the bias (the mean difference in paired SpO2 and SaO2 samples), precision (standard deviation of the difference), and accuracy (root mean squared error, ARMS*) for both groups. They found a negative bias of 0.20% for black subjects, compared to a negative bias of 0.05% for white subjects, a difference of 0.15% (p < 0.001), which is not clinically significant and is numerically indistinguishable because the SpO2 display resolution is 1% on commercially available pulse oximeters (both from Masimo and other manufacturers). They found precision of 1.40% for black subjects and 1.35% for white subjects. Accuracy (ARMS) was 1.42% for black subjects and 1.35% for white subjects. These results are consistent with the accuracy specifications of RD SET sensors (1.5% accuracy ARMS).
By comparison to the Masimo finding of 0.15% difference in bias between black and white subjects, the 2020 letter to the editor reported a difference in bias of 8.1% in a cohort of black and white hospital patients2 – 54 times higher than the Masimo result.
Masimo is conducting additional studies and will report its findings in the future.
- Barker SJ, Wilson WC. Accuracy of Masimo SET® Pulse Oximetry in Black and White Volunteer Subjects: A Retrospective Review. Annual Meeting of the Society of Technology in Anesthesiology. Presented Jan 15, 2022.
- Sjoding MW, et al: Racial Bias in Pulse Oximetry Measurement N Engl J Med 2020; 383 (25):2477-2478.
- Valbuena VSM, et al: Racial Bias in Pulse Oximetry Measurement Among Patients About to Undergo ECMO in 2019-2020, A retrospective Cohort Study. Chest 2021 Sep 27; S0012-3692(21)04065-4.