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[Pages:3]Fact Sheet

CSF Xanthochromia

Clinical information

CSF Xanthochromia may be useful in patients suspected of subarachnoid haemorrhage (SAH) but no evidence on CT scan. CSF Xanthochromia refers to a yellow discolouration of CSF as a result of the presence of bilirubin. As a result of SAH, red cells present in the CSF release oxyhaemoglobin, which is then converted to bilirubin in vivo. This process is time dependent, and CSF should be collected at least 12 hours following the suspected event for adequate sensitivity. CSF bilirubin may remain increased for up to 2 weeks. In the initial few days following subarachnoid haemorrhage, oxyhaemoglobin and bilirubin are usually both detected, and as time progresses and oxyhaemoglobin is converted to bilirubin, bilirubin alone may be present.

Interpretation of results

Bilirubin and oxyhaemoglobin are measured by spectrophotometry and reported, together with an interpretive comment, as the net absorbance detected at a characteristic wavelength (net bilirubin absorbance (NBA) and net oxyhaemoglobin absorbance (NOA)).

Increased bilirubin and oxyhaemoglobin (NBA > 0.007 AU and NOA > 0.02 AU with visible oxyhaemoglobin peak) is consistent with a SAH.

Increased bilirubin (NBA > 0.007 AU) with no increase in oxyhaemoglobin may be consistent with a SAH, although this would be unusual within the first week after the suspected event. With these results potential confounding effects of an increased serum bilirubin or CSF protein should be considered. An increased CSF bilirubin may be due to an increased serum bilirubin, and as such in patients with a serum bilirubin >20 umol/L the NBA is adjusted for this using a formula to give an adjusted value. An increase in CSF protein may also be accompanied by an increase in CSF bilirubin when there is a breakdown of the blood-brain barrier (e.g. in meningitis). Therefore in patients with a CSF protein >1g/L, an increase in CSF bilirubin, without oxyhaemoglobin should be interpreted with caution.

There is no evidence to support SAH in patients without increased CSF bilirubin or significant oxyhaemoglobin. In patients with significant oxyhaemoglobin it is not possible to exclude SAH as this may obscure the detection of CSF bilirubin due to overlap of the photometric spectrum of these molecules.

Cautions

Potential False negative results: Collection < 12 hours following the suspected event may not allow enough time for bilirubin to become detectable Exposure of the sample to light as this degrades bilirubin

CHEMAI - CSF Xanthochromia Fact Sheet - 01 Authorised: AR Horvath

Prepared: P Stanford

Page 1 of 3 Released: 08.05.2018

Fact Sheet

CSF Xanthochromia

High oxyhaemoglobin absorbance may obscure the net bilirubin absorbance such that it is not detectable.

Potential false positive results: Increased bilirubin may also be detected in the CSF when the CSF total protein is raised, or serum bilirubin is increased. The presence of blood from a previous traumatic tap may result in the presence of oxyhemoglobin and bilirubin confounding the interpretation of subsequent CSF collection.

Specimen:

Sample type: CSF

Minimum volume: 1 mL ideal (0.5 mL minimum)

Collection requirements: CSF for xanthochromia testing should be collected a minimum of 12 hours after the suspected event. Please indicate on the request form the clinical indication, the time of onset of symptoms/suspected event, time of lumbar puncture and result of CT scan. To avoid contamination from red cells as a result of the trauma from the lumbar puncture, CSF taken for xanthochromia should be collected into a separate container to those in which the first few mL of fluid are placed. This should be at least the third, or ideally the fourth sample. Protect this sample from the light.

Label specimens sequentially: - First specimen: 0.5 mL CSF (approximately 10 drops) placed in a sterile universal CSF container for measurement of glucose and protein (required for interpretation of xanthochromia). - Second/third specimens: 5 mL of CSF divided into two sterile universal containers collected sequentially for microbiology. This volume is provided as a guide and is sufficient for commonly required microbiology tests, however for more specialised tests, or where this volume is not able to be collected please refer to the required volume for individual tests or contact microbiology. - Fourth specimen: 1 mL CSF (approximately 20 drops) in a sterile universal container for xanthochromia and protect it from light (wrap sample in aluminium foil)

Samples should be delivered to the laboratory as soon as possible

A simultaneous blood specimen should be taken for serum bilirubin and total protein measurement as these are needed to assist in interpretation.

Method: Spectrophotometry

Testing frequency: Available 24 hours a day.

CHEMAI - CSF Xanthochromia Fact Sheet - 01 Authorised: AR Horvath

Prepared: P Stanford

Page 2 of 3 Released: 08.05.2018

Fact Sheet

CSF Xanthochromia

Reference: Cruickshank et al. Revised national guidelines for analysis of CSF for bilirubin in suspected SAH. Ann Clin Biochem 2008; 45: 238?244.

Enquiries:

NSW Health Pathology Department of Clinical Chemistry and Endocrinology The Prince of Wales Hospital

Rita Horvath Clinical Director Tel 02 9382 9078 Mob 0404 027 843 andrea.horvath@health..au

Phoebe Stanford Clinical Chemistry Registrar Tel 02 9382 1524 Mob 0429537546 phoebe.stanford@health..au

CHEMAI - CSF Xanthochromia Fact Sheet - 01 Authorised: AR Horvath

Prepared: P Stanford

Page 3 of 3 Released: 08.05.2018

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