CSF spectrophotometry in the diagnosis of subarachnoid haemorrhage
- R Beetham1,
- M N Fahie-Wilson1,
- I Holbrook1,
- P Thomas1,
- A M Ward1,
- I D Watson1,
- P R Wenham1,
- P A E White1
- 1Advisory group to UK NEQAS for CSF Proteins and Biochemistry, UK NEQAS, Department of Immunology, Sheffield S5 7YT, UK; robert.beetham@north-bristol.swest.nhs.uk
We note with interest the recent “Best Practice” article on cerebrospinal fluid (CSF) spectrophotometry in the diagnosis of subarachnoid haemorrhage (SAH) by Dr Cruickshank.1 As a group that has produced a set of proposed national guidelines for the practice of spectrophotometry,2 we wish to highlight several important differences between the two sets of recommendations.
Most importantly, Dr Cruickshank concludes that, as long as a CSF sample containing up to 40 000 × 106 erythrocytes/litre is centrifuged within 15 minutes, no oxyhaemoglobin will be seen in the supernatant after centrifugation, and that within this cell count and time constraint, the presence of oxyhaemoglobin in CSF is supportive of SAH. This is entirely consistent with her in vitro data,3 although the only practical way of achieving CSF delivery within this time would appear to be by pneumatic tube, itself a cause of artefactual haemolysis.4 However, there are other in vitro data that allow for a longer time lapse before centrifugation. …
