Patients presenting with sudden severe headache may have a subarachnoid haemorrhage (SAH). After a normal head computer tomography (CT), a lumbar puncture is routinely performed to rule out SAH. Photospectrometry is then used to detect bilirubin in cerebrospinal fluid (CSF). Photospectrometric analysis of CSF reaches a high sensitivity, but a low specificity for SAH. This low specificity necessitates extensive additional research to rule out cerebral aneurysm accompanied by high costs and risk of complications.