Specificity of elevated cerebrospinal fluid bilirubin in the investigation of subarachnoid haemorrhage

Background The spectrophotometric examination of cerebrospinal fluid for bilirubin is an established investigation in patients with suspected subarachnoid haemorrhage. This study assesses the diagnostic specificity of an elevated cerebrospinal fluid bilirubin and how this may be influenced by the presence of oxyhaemoglobin and the concentration of cerebrospinal fluid total protein. Methods One thousand cerebrospinal fluid spectroscopy reports were reviewed. Electronic patient records were examined to determine the clinical outcome in patients with an elevated cerebrospinal fluid bilirubin. Results Forty-four out of 1000 cerebrospinal fluid scans showed an increase in cerebrospinal fluid bilirubin unrelated to elevated serum bilirubin concentrations. This was associated with subarachnoid haemorrhage in 16 (36%) cases. Subarachnoid haemorrhage was confirmed in 5/17 (29%) patients positive for cerebrospinal fluid bilirubin alone and in 11/27 (41%) patients positive for both cerebrospinal fluid bilirubin and oxyhaemoglobin. At cerebrospinal fluid total protein concentrations