Measurement of Hemoglobin in Unlysed Blood by Near-Infrared Spectroscopy

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Abstract
Visible and near-infrared transmittance ( T) spectra of unlysed blood samples were obtained with an NIRSystems Model 6500 spectrophotometer modified for an open cell and a vertical light path. Without rigid control of the pathlength and temperature, we were able to measure hemoglobin content within a standard error of 0.43 g/dL using a single-term second-derivative ratio of log(1/ T) data at 1740 and 1346 nm. Calibration was done on a set of 104 samples (two spectra of blood from 52 patients) having hemoglobin levels of 6.1 to 19.2 g/dL. Validation was done on an independent set of 56 samples (two spectra of blood from 28 patients) having hemoglobin levels of 7.2 to 19.0 g/dL. The reproducibility of the measurement, tested by computing the coefficient of variability of the 28 duplicated results, was 0.63% (<0.1 g/dL). The results demonstrate a rapid simple diffuse transmittance measurement of hemoglobin in unlysed blood.