Evaluation of revised UK-NEQAS CSF-xanthochromia method for subarachnoid hemorrhage: outcome data provide evidence...

Subarachnoid haemorrhage (SAH) has a high morbidity and mortality and requires prompt diagnosis. In patients with negative findings on computed-tomogram of the brain (CT-Brain) cerebrospinal fluid (CSF)-xanthochromia is considered the test of choice if performed 12 h or more after symptom onset. We audited the accuracy, usefulness and timing of CSF-xanthochromia testing and the interpretation of equivocal CSF-xanthochromia findings. We also investigated mortality outcomes for defined subsets of patients.

A retrospective audit of CSF-xanthochromia tests over 8 years was performed. The service uses the revised UK-NEQAS (United Kingdom National External Quality Assessment Service) method.

We analysed 543 cases (F=299, median age 44yrs) with 19 cases (3.5 %) having SAH. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of CSF-xanthochromia testing were 100 , 98.1, 65.9, 100 % respectively (equivocal results were counted as positives). 280 cases (F=153, median age 43yrs) had LP performed more than 24 h after the onset of headache (median time to LP=72 h). The sensitivity and specificity of the CSF-xanthochromia were 100 and 97.4 % in this group with NPV 100 % and PPV 66.6 %. 183 (65.4 %) CSF-xanthochromia negative cases in this subgroup had follow up data and survived without SAH occurring in the 12 months follow up.

In this study, supported by followup outcome data, we show that CSF-xanthochromia testing using the revised UK-NEQAS method is fit-for-purpose for the use as a second line test to exclude SAH in patients with negative CT-brain including delayed presentation more than 24 h after headache onset.