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The literature search for this review was based on the intention to include all up-to-date studies to accurately describe the current scientific basis for CSF-based diagnostics of SAH and to illustrate the variability in methods between countries.
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In this review, we aim to discuss available CSF methods for SAH diagnosis, clarify their strengths and weaknesses, and outline their use on a global scale, focusing on recent guidelines and experiences from laboratory medicine in the UK, Germany, Sweden, the Netherlands, Austria, and the USA. There is no definite international consensus on a preferred diagnostic algorithm, and procedures differ between countries and regions, which may have an impact on patients in terms of diagnosis, treatment, and prognosis. Tools for SAH diagnosis include imaging and cerebrospinal fluid (CSF) analyses. Typical initial symptoms are severe headache with a sudden onset (“thunderclap headache”), neck stiffness, vomiting, confusion, or loss of consciousness. In the majority of cases, SAH is caused by a spontaneous rupture of an aneurysm in the arterial circulation of the brain. Importantly, SAH both has a high fatality (30%–70%) and may occur at an early age compared with other causes of stroke. Subarachnoid haemorrhage (SAH) accounts for approximately 5% of all strokes and has a yearly incidence of approximately 1 in 10,000 persons. Keywords: bilirubin cerebrospinal fluid diagnosis haemoglobin subarachnoid haemorrhage Introduction Where spectrophotometry is not available, the combination of CSF cytology for erythrophages or siderophages and ferritin is a promising alternative. A positive finding of CSF bilirubin is a strong indicator of an intracranial bleeding, whereas a positive finding of CSF oxyhaemoglobin may indicate an intracranial bleeding or a traumatic tap. Visual inspection of CSF for xanthochromia is still frequently used for diagnosis of SAH, but it is advised against because spectrophotometry has a superior diagnostic accuracy. There is a consensus that spectrophotometry has the highest diagnostic performance, but both oxyhaemoglobin and bilirubin determinations are susceptible to important confounding factors. The methods vary in availability and performance. CSF analyses for SAH include visual examination, red blood cell counts, spectrophotometry for oxyhaemoglobin or bilirubin determination, CSF cytology, and ferritin measurement. The principle literature search was conducted using PubMed and Scopus with the search items “cerebrospinal fluid”, “subarachnoid haemorrhage”, and “diagnosis”. Here, we summarize the scientific evidence for different CSF methods for SAH diagnosis and describe their implementation in different countries. Diagnostic cerebrospinal fluid (CSF) analyses may be performed after a negative computed tomography scan, but the precise analytical methods to be used have been debated. Early SAH diagnosis allows the early treatment of a ruptured cerebral aneurysm, which improves the prognosis. Subarachnoid haemorrhage (SAH) has a high mortality and morbidity rate.