Improved quantification of CSF bilirubin in the presence of hemoglobin using least squares curve-fitting.

Subarachnoid hemorrhage (SAH) is a dangerous neurological event with a very short time window for early diagnosis. Clinical diagnoses performed in a lab seek to quantify bilirubin in cerebrospinal fluid (CSF) as a biomarker for SAHs; however laboratory assays suffer from lengthy protocols, interference from hemoglobin, and the availability of expertise. Substantial improvements in the determination of bilirubin concentration in the presence of hemoglobin in CSF are demonstrated in this work. Concentration estimates within 15% for bilirubin in the range of 0.2 to 1.6 mg /dl were determined for CSF samples containing fresh hemoglobin concentrations ranging from 0.05 to 0.25 g/dl. To demonstrate extensibility of the system with respect to more complete mock SAH samples, sample sets with one additional species of both hemoglobin and bilirubin, methemoglobin and alpha-bilirubin, respectively, were tested and yielded results within 25% of actual values, as measured by standard chemical assays of preparations prior to mixing.