Synonyms

CSF xanthochromia

Clinical Indications

The test is performed to try and identify patients who have had a subarachnoid haemorrhage (SAH) but in whom the CT scan is negative. After SAH, haemolysis of subarachnoid erythrocytes releases haemoglobin, which is converted to bilirubin. Bilirubin concentration reaches a maximum at about 48 hours and may last for 2 to 4 weeks after extensive bleeding. Because the formation of bilirubin after haemorrhage is a time-dependent process, CSF must be sampled at least 12 hours after a suspected event.

Request Form 

Combined Pathology Blood form (Yellow/Black or Blue for GP's)

Availability

On request.

Specific Criteria

The following must be indicated on the request form:
 - Clinical indication for request
 - Result of CT scan
 - Time of onset of symptoms/event
 - Time of lumbar puncture
 - If the differential diagnosis includes meningitis

Patient Preparation

CSF must be sampled at least 12 hours after a suspected event.

Turnaround Time

Within 24 hours

Specimen

CSF collected sequentially (the first few ml. of fluid should not be used for this investigation). The first fraction should be collected into a grey top fluoride tube for glucose. CSF may also be required for microbiology and should be collected next (3 fractions into 3 white capped universals). The specimen for spectrophotometry must be the last fraction taken and ideally, at least the 4th. A blood sample (yellow top SST) should be taken at the same time for bilirubin, total protein and glucose.

Volume

Minimum of 1 ml.

Container

White Capped Universal

Collection

Sample should be protected from light and transported to Clinical Biochemistry immediately. Do not use the pneumatic tube system.

Lab. Handling

Centrifuge CSF sample as soon as possible after receipt and within 1 hour of collection. Store supernatant in the dark at 4C until analysis. (CSPEC & analyse; NOCSF & save)

Causes for Rejection

CSF sample taken less than 12 hours after suspected event.
Insufficient information regarding timing of sample.
Delay in sample reaching laboratory

Interpretation

The report will consist of an interpretation:
Not consistent with SAH (low CSF bilirubin relative to serum)
Consistent with SAH or other source of CSF blood (increased CSF bilirubin relative to serum with normal CSF protein)
Consistent with SAH, other source of CSF blood or increased bilirubin accompanying increased CSF protein - interpret results with caution (increased CSF bilirubin relative to serum with increased CSF protein)