Comparison of Masimo Rad-67 SpHb non-invasive hemoglobin monitoring device with complete blood count measurement for use in pregnancy: An observational multi-site cohort study

BackgroundAnemia remains a major health concern, particularly during pregnancy. However, blood draws, laboratory capacity, processing time, and equipment cost required for hemoglobin testing to diagnose anemia can be prohibitive. The Total Hemoglobin SpHb Rad-67 Pulse CO-Oximeter offers a non-invasive, portable, and affordable point-of-care alternative. We aimed to validate SpHb against complete blood count (CBC) in a pregnant and postpartum population. MethodsThis was a substudy of the Pregnancy Risk, Infant Surveillance, and Measurement Alliance (PRISMA) Maternal and Newborn Health Study. A total of 2,700 participants in Zambia, Kenya, and Pakistan provided hemoglobin measurements both by CBC and the Rad-67 Masimo SpHb device at four visits during pregnancy and at six-weeks postpartum. We assessed agreement between SpHb and CBC and used mixed models to identify factors that explained or influenced differences between the two methods. ResultsWe found the mean hemoglobin measurement by SpHb (12.8{+/-}1.6 g/dL) was higher than by CBC (11.0{+/-}1.6 g/dL). However, this overall positive bias masked systematic misclassification at the extremes: SpHb overestimated values among women with very low hemoglobin (Mean Difference (MD) =-3.95; 95%CI-4.28,-3.62) and underestimated values at very high hemoglobin levels (MD = 2.44; 95%CI 2.14, 2.74), even after adjustment. Using CBC, 48% of observations were classified as anemic (<11 g/dL), compared to 9% by SpHb; conversely, just 7% of CBC readings fell within 13-15 g/dL, compared to 38% by SpHb. Agreement metrics consistently showed poor concordance between the two methods. ConclusionsSpHb systematically overestimated hemoglobin on average and showed poor agreement with CBC, particularly at clinically relevant extremes. Until greater accuracy of SpHb is demonstrated in this population, hemoglobin testing with laboratory-based methods is recommended to inform clinical decision-making in pregnancy. AUTHOR SUMMARYAnemia is a major global health challenge linked with maternal morbidity, adverse birth outcomes, and impaired infant development. Accurate and accessible hemoglobin testing is critical for timely anemia diagnosis and treatment. The gold standard for hemoglobin testing is complete blood count using venous blood; however, this method requires laboratory infrastructure, blood sample collection, and trained personnel, limiting feasibility in low-resource and rural settings where anemia burden is highest. We evaluated the accuracy of the Masimo Total Hemoglobin SpHb(R) measured by Rad-67(R) Pulse CO-Oximeter(R): a device that measures hemoglobin via an optical sensor placed on the patients finger. We found the mean hemoglobin measurement by SpHb (12.8{+/-}1.6 g/dL) was higher than by CBC (11.0{+/-}1.6 g/dL).We found that the Masimo device consistently overestimated hemoglobin at very low levels and underestimated at very high levels. Masimo SpHb classified 9% of women as anemic (i.e. hemoglobin <11 g/dL), compared to 48% using the gold standard method. The Masimo SpHb was even less accurate for women later in gestation, living with HIV, and who reported using betelnut, tobacco, or smoking. Device improvements or software-based correction factors are needed to improve performance of the Total Hemoglobin SpHb Rad-67 Pulse CO-Oximeter before it can be used to measure hemoglobin in pregnancy.