Point-of-care noninvasive hemoglobin determination using fiber optic reflectance spectroscopy

Rapidly identifying anemia through qualitative observation of the palpebral conjunctiva for pallor is standard medical practice. We report on the ability of using a fiber optic array probe to collect diffusely reflected light from the palpebral conjunctiva and measure hemoglobin concentration noninvasively. Patients (N=102) admitted to the emergency department and receiving a complete blood count (CBC) were enrolled as a convenience set. The tarsal plate was exposed by averting the lower eyelid and illuminated with a white LED while diffusely reflected light was collected using a fiber optic probe and commercial grating spectrometer. Spectra were analyzed using partial least squares regression to extract hemoglobin concentration information and compare to the CBC result. The probe and algorithm demonstrated correlation coefficient of r = 0.82 and standard error of 1.05 g/dL compared to invasive CBC test. Experimental error is due to variability in distance and position of the probe relative to the conjunctiva. This technique has shown the ability to measure total hemoglobin noninvasively and in real-time at the point-of-care using diffuse reflectance spectroscopy of the tarsal plate, leading to potential inclusion of this class of device as a triage centric tool to identify anemia appearing with internal hemorrhage or other acute conditions.