Regarding the use of spectrophotometry for the diagnosis of subarachnoid
haemorrhage there is a considerable body of literature supporting its use.
A summary (Vermeulen & van Gijn, J Neurol Neurosurg Psych 1990;53:365-372)
supports the use of spectrophotometry as long as the sample is taken more
than 12 hours after the presumed onset and centrifuged and any red cells
removed within 1-2 hours of collection.
The current controversy regards what constitutes xanthochromia? Earlier
authors suggest haemoglobin (a peak at 415nm) or bilirubin (a peak at 450
nm) are both markers in a sample collected and treated as above, although
the use of haemoglobin as a marker has now been questioned (Beetham et al,
Ann Clin Biochem 1998;35:1-4). The use of bilirubin alone as the marker is
supported by Chalmers and Kiley (Clin Chem 1998;44:1740-2) who correct for
the effects of haemoglobin on the height of the bilirubin peak.
In particular these groups agree that "three tube methods" are inadequate
for the distinction between SAH and traumatic tap.
Graham Jones
Staff Specialist in Chemical Pathology
St Vincent's Hospital Sydney
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