Revised national guidelines for the analysis of cerebrospinal fluid for bilirubin in suspected subarachnoid haemorrhage

In the revised national guidelines for cerebrospinal fluid (CSF) spectroscopy, the significance of an increased CSF bilirubin concentration has been emphasized and the reporting guidelines adjusted accordingly. ¹ In her commentary on the new guidelines Anne Cruickshank emphasized that some comments were modified in order to avoid confusing clinicians by introducing unnecessary or confusing information which is commendable. ² The revised guidelines also emphasize the low diagnostic significance of detectable oxyhaemoglobin and yet, in the reporting flowchart the finding of oxyhaemoglobin is considered sufficient reason to no longer apply a correction to CSF bilirubin in a jaundiced patient. The possibly unintended consequence is that no matter how high the plasma bilirubin, an unambiguous statement will be issued ‘Consistent with SAH’, which will lead the clinician to believe that there is no uncertainty about the significance of the CSF findings, which is just as inappropriate as providing an interpretation which is ambiguous. No evidence has been provided to support this approach or counter the strongly argued case for such a correction being appropriate. ³ If the most suitable method for correcting a high plasma bilirubin cannot be agreed, I believe it would be better in this situation to discuss the results with the clinicians so that they have a proper understanding of the limitations of the analysis. Clinicians are used to coping with uncertainty and may have other strategies for achieving a diagnosis and managing their patient. This should be recognized in the way in which we report results in difficult cases and we should not mislead by overstating the significance of the findings.