Precision and accuracy of noninvasive hemoglobin measurements during pregnancy

Introduction: The NBM-200 is a novel device allowing noninvasive hemoglobin measurement. The system is based on occlusion spectroscopy technology in the red/near-infrared range. At the core of this technology is the production of a new bio-physical signal, resulting from temporarily occluding the blood flow in the measurement site. The measurement is performed using an annular, multi-wavelength probe with pneumatically operated cuffs, with which an over-systolic pressure is produced at the finger base. Methods: OrSense NBM200 was tested during the years 2011-2012 in a population of pregnant women. Upon receipt of informed consent, two noninvasive Hemoglobin measurements were performed on the right and left thumbs of each subject. Reference hemoglobin values were obtained from venous blood samples drawn at the same time of the noninvasive measurement. Blood Hemoglobin was evaluated on an LH-750 Beckman Coulter counter, acting as the reference "gold standard." Results: A total of 126 data pairs were obtained in the trial from 63 women. The mean error (bias) of the NBM200 readings compared to the reference was 0.1-g/dL and the accuracy, defined as the standard deviation of error, was 0.86-g/dL. A Bland-Altman comparison of the NBM200 versus the Coulter device shows that the 95% limits of agreement is -1.59 to 1.79-g/dL. Conclusion: Our study demonstrates a good correlation between reference blood hemoglobin and noninvasive hemoglobin measurements. The NBM-200 can accurately assess hemoglobin levels, in a noninvasive fashion, during pregnancy.