Cerebrospinal fluid total protein cannot reliably distinguish true subarachnoid haemorrhage from other causes of raised cerebrospinal fluid net bilirubin and net oxyhaemoglobin absorbances.
BACKGROUND
In cerebrospinal fluid (CSF) spectrophotometry, if the net bilirubin absorbance (NBA) and net oxyhaemoglobin absorbance (NOA) are both raised with a visible oxyhaemoglobin peak, the revised national guidelines for analysis of CSF bilirubin advise interpreting the results as 'Consistent with subarachnoid haemorrhage (SAH)' regardless of the CSF total protein concentration of the specimen. We wanted to study the range of CSF total protein concentrations found in confirmed SAH to establish if the CSF total protein value can give further guidance on the likelihood of SAH.


METHODS
Consecutive cases from five different hospital sites were included if the CSF NBA was greater than 0.007 AU and the NOA was greater than 0.02 AU with a visible oxyhaemoglobin peak. For the cases identified, the laboratory information management system and patient records were interrogated to identify the total protein concentration of the CSF specimen and whether SAH had ultimately been confirmed or excluded by other methods and supporting evidence.


RESULTS
Results from 132 patients were included. The CSF total protein range in confirmed SAH was 0.23-3.08 g/L with a median concentration of 0.7 g/L (n = 51). In the SAH excluded group, the CSF total protein range was 0.43-29 g/L with a median concentration of 1.9 g/L (n = 81).


CONCLUSIONS
Although confirmed SAH was not associated with the very highest concentrations of CSF total protein, a definite CSF protein cut-off concentration above which SAH could reliably be excluded cannot be recommended.
Department of Neurobiochemistry and Neuroimmunology, The Walton Centre, Liverpool, UK katherine.birch@thewaltoncentre.nhs.uk.
Katherine
K
Birch
Department of Blood Sciences, Stepping Hill Hospital, Stockport, UK.
Gillian
G
Burrows
Department of Biochemistry, Southern General Hospital, Glasgow, UK.
Anne
A
Cruickshank
UK NEQAS for Immunology, Immunochemistry & Allergy, Northern General Hospital, Sheffield, UK.
William
W
Egner
Department of Clinical Biochemistry, York Hospital, York, UK.
Ian
I
Holbrook
Department of Blood Sciences, Countess of Chester Hospital, Chester, UK.
Emma
E
Lewis
Department of Biochemistry, Southern General Hospital, Glasgow, UK.
Jane
J
McNeilly
UK NEQAS for Immunology, Immunochemistry & Allergy, Northern General Hospital, Sheffield, UK.
Dina
D
Patel
Department of Neuroimmunology, National Hospital for Neurology & Neurosurgery, London, UK.
Viki
V
Worthington
D001663:Bilirubin / Q000134:cerebrospinal fluid*; D002556:Cerebrospinal Fluid Proteins / Q000032:analysis*; D006801:Humans; D010108:Oxyhemoglobins / Q000134:cerebrospinal fluid*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D013345:Subarachnoid Hemorrhage / Q000134:cerebrospinal fluid* / Q000175:diagnosis*
D002556:Cerebrospinal Fluid Proteins; D010108:Oxyhemoglobins; D001663:Bilirubin
Bilirubin; analytes; clinical studies; laboratory methods; neurological disorders; spectroscopy