BILIRUBIN, FERRITIN, D-DIMERS AND ERYTHROPHAGES IN THE CEREBROSPINAL-FLUID OF PATIENTS WITH SUSPECTED SUBARACHNOID HEMORRHAGE BUT NEGATIVE COMPUTED-TOMOGRAPHY SCANS

Aim-To assess the diagnostic value of cerebrospinal fluid (CSF) spectr ophotometry, cytology, ferritin, and D-dimer measurements in the inves tigation of suspected subarachnoid haemorrhage in patients with negati ve or equivocal computed tomography (CT) scans. Methods-CSF specimens submitted for assessment of xanthochromia were examined for erythropha ges using a cytospin preparation stained with Wright's stain, for ferr itin using the Ciba-Corning Magic IRMA assay, D-dimers using the Dimer test 2 latex agglutination slide test, and for bilirubin by scanning s pectrophotometry. The patients were divided into three groups for data analysis and the results compared with the existing methods, CT, and angiogram results. Final diagnoses were reviewed by a consultant neuro logist. Results-Thirty six patients were recruited. In those patients with confirmed subarachnoid haemorrhage CSF cytology had a low sensiti vity and there were false negative results with both the D-dimer and f erritin assays. Eleven patients with a negative or equivocal CT scan u nderwent angiography, but only one aneurysm and no arterio-venous malf ormations or bleeding points were identified. In the patient with the aneurysm there was no laboratory evidence of subarachnoid haemorrhage. Six patients had CSF abnormalities detected by the special tests only and in none of these cases was subarachnoid haemorrhage confirmed. Ah results were normal in four out of five cases of traumatic tap. Concl usions-This is a small study, but it shows that, depending on the timi ng of the lumbar puncture, false negative results can occur with both ferritin and D-dimer measurements. It suggests that neither of these t ests adds significantly to the information provided by CT, visualisati on of CSF, and spectrophotometry and confirms that, despite the use of spectrophotometry, D-dimer and ferritin assays in selecting patients for angiography, the proportion of patients with negative CT scans and colourless CSF with demonstrable vascular lesions remains low.