Diagnosis of late presenting subarachnoid hemorrhage: Comparison of methods for cerebrospinal fluid ferritin

Abstract

Background. The majority of subarachnoid hemorrhage (SAH) is diagnosed using imaging techniques. The sensitivity of computed tomography scans decreases with increasing time after the bleeding event which can lead to false negative CT scans. Spectrophotometry and microscopic investigations of the cerebrospinal fluid (Csf) can provide additional diagnostic support, but may not be available for emergency diagnoses. Csf-Ferritin has been suggested as an alternative additional marker for SAH that present late and has a potency to be measured in a routine laboratory. Methods. A routine Ferritin chemiluminescent assay (Dimension Vista) was compared with a branded and CE-marked Csf-Ferritin nephelometric assay (BN ProSpec) using surplus routine patient samples. We calculated imprecision at pertinent concentrations, compared patient samples, and established reference intervals. Results. The standard deviation was about a third for the Dimension Vista assay compared to that of the BN ProSpec assay at the three tested concentrations. The correlation showed a systematic difference between the methods but the correlation was high (r = 0.955). Accordingly, the reference intervals were higher for the BN ProSPec (2.7–16.8 μg/L) than for the Dimension Vista (2.0–12.6 μg/L). Conclusion. The precision of the Dimension Vista measurements was considerably better than that of the BN ProSpec. The Dimension Vista results correlated well with those of the comparative method, yielding slightly lower values. This is reflected in the reference intervals. These findings permit the use of the routinely available Ferritin assay of the Dimension Vista for measuring Csf-Ferritin and complementing the late diagnosis of SAH outside office hours of specialized Csf laboratories.