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Iterative model for the calculation of oxyhemoglobin, methemoglobin, and bilirubin in absorbance spectra of cerebrospinal fluid.

The measurement of the blood pigments oxyhemoglobin, methemoglobin, and bilirubin in cerebrospinal fluid (CSF) has been useful in the differential diagnosis of various hemorrhagic and traumatic disorders of the brain (1)(2)(3)(4)(5)(6)(7)(8)(9). Computed tomography often is used for the detection of a hemorrhage, although small vascular bleedings can remain undetectable, in which case the measurement of blood pigments in CSF might be helpful (4)(6)(7). Detection and quantification of the blood pigments from the absorbance spectra are, however, difficult, and attempts to quantify these pigments (1)(10)(11) were not very successful because of factors such as turbidity, pH variability (11), and the large overlap of the absorbance curves, especially those of oxyhemoglobin and methemoglobin (1)(2)(12). The results of the visual interpretation of the spectra are qualitative in nature and depend strongly on the experience of the technicians; results, therefore, are prone to large inter- and intraindividual variation. Our aim was to develop a standardized method for the spectrophotometric examination of CSF and to obtain reliable quantitative results.

A solution to this problem was found in the mathematical step-by-step (iterative) unraveling of the main absorbance scan into the scans of the individual blood pigments via the iterative process.

On arrival at the laboratory, the CSF samples were centrifuged for 10 min …