Visual inspection versus spectrophotometry in detecting bilirubin in cerebrospinal fluid
- 1Department of Neurology, University Medical Centre Utrecht, Utrecht, Netherlands
- 2Department of Clinical Chemistry, University Medical Centre Utrecht
- 3Julius Centre for Clinical Sciences and Primary Care, University Medical Centre Utrecht
- Correspondence to: Dr F H H Linn Department of Neurology, University Medical Centre/Central Military Hospital, Heidelberglaan 100, 3584 CX Utrecht, Netherlands;
- Received 12 August 2004
- Accepted 9 February 2005
- Revised 30 January 2005
Objectives: To compare the diagnostic accuracy of visual inspection and spectrophotometry for identifying the presence of bilirubin in the cerebrospinal fluid (CSF).
Methods: Clinicians and students assessed CSF specimens with seven degrees of extinction between 0.00 and 0.09 at 450–460 nm as “yellow,” “doubtful,” or “colourless” after random presentation under standard conditions. The assessments were compared with spectrophotometry, with 0.05 being taken as the cut off level for the presence of bilirubin. Results were compared between the two groups and explored by means of receiver operating characteristic (ROC) curves.
Results: All 51 clinicians and 50 of 51 students scored the tubes with extinction of 0.06 or higher as “yellow” or “doubtful.” Tubes without any bilirubin were scored as “yellow” by three of the students only. The ROC curves confirmed that the diagnostic properties of the visual inspection versus spectrophotometry were slightly better for the clinicians than for the students.
Conclusions: If CSF is considered colourless, the extinction of bilirubin is too low to be compatible with a diagnosis of recent subarachnoid haemorrhage. If CSF is not considered colourless, spectrophotometry should be carried out to determine the level of extinction of bilirubin.
Competing interests: none declared