Annals of Clinical Biochemistry > Volume 45, Number 2 > Pp. 189-192

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Original Article

What is the role of cerebrospinal fluid ferritin in the diagnosis of subarachnoid haemorrhage in computed tomography-negative patients?

Ian D Watson ¹, Robert Beetham ² , Michael N Fahie-Wilson ³, Ian B Holbrook ⁴ and Daniel M O'Connell ¹

¹ Department of Neurobiochemistry, The Walton Centre for Neurology and Neurosurgery, Liverpool L9 7LJ, UK; ² Department of Clinical Biochemistry, North Bristol NHS Trust, Frenchay Hospital, Bristol BS16 1LE, UK; ³ Department of Biochemistry, Southend Hospital, Westcliff on Sea, Essex SS0 0RY, UK; ⁴ Department of Clinical Biochemistry, York Hospital, York YO31 8HE, UK

Corresponding author: Dr Robert Beetham. Email: robert.beetham{at}nbt.nhs.uk

Background: Spectrophotometry of cerebrospinal fluid (CSF) for bilirubin is the recommended method for investigation in suspected cases of subarachnoid haemorrhage (SAH), when a computed tomography (CT) of the head is negative for blood. There is a potential need for a simpler alternative. Measurement of CSF ferritin might fulfil this need.

Method: We have measured ferritin in the CSF from 252 patients with suspected SAH who were negative on a CT of the head for blood, recruited on a consecutive intention to recruit basis from four centres. CSF spectrophotometry was performed on all samples. A positive outcome was taken as an aneurysm found on angiography that was treated or a discharge diagnosis of non-aneurysmal SAH.

Results: A final diagnosis of aneurysmal SAH was made in six patients, an arteriovenous malformation in one and non-aneurysmal SAH in nine. Receiver operating characteristic (ROC) analysis showed that at 6.4 µg/L, sensitivity, specificity, positive and negative predictive values were 1.0, 0.48, 0.12 and 1.0, respectively. At 12 µg/L, these values were 0.81, 0.91, 0.38 and 0.98, respectively.

Conclusions: At an appropriate negative predictive value (1.0) for a rule-out test, ferritin has too low a specificity to function as a stand-alone test and we cannot recommend it as an initial screen to be followed by spectrophotometry.

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