Annals of Clinical Biochemistry > Volume 45, Number 6 > Pp. 617-618

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Letters

Revised national guidelines for analysis of CSF for bilirubin in suspected SAH

We are pleased to see the evolution of the UK guidelines in this area (Ann Clin Biochem 2008;45:238–244), although contest the view that analysis of bilirubin in CSF using diazo methods has not been adequately validated in this context and should not be used.¹ We developed such an approach to diagnosis,^2,3 now used routinely in our laboratory to identify approximately 90% of samples that do not need to be submitted to spectrophotometry. Our approach employs the measurement of CSF bilirubin on an automated instrument, using the Jendrassik and Gróf method, calibrated to measure lower concentrations.² We found that at a CSF bilirubin cut-off of 359 nmol/L, based on our upper reference interval in CSF, there was 100% negative predictive value² for a net bilirubin absorbance greater than 0.007, i.e. positive initial scan. In a follow-up study,³ the validity of this cut-off was confirmed, with no evidence from clinical records to suggest that any case of SAH had been missed. The accompanying editorial,⁴ acknowledged that it could thus act as an initial screening method to eliminate those samples that would subsequently prove to be negative spectrophotometrically, thereby allowing the majority of samples to be screened out by a procedure potentially available on a 24-hour basis. An added advantage is that small volumes of sample, around 100 µL (compared with 0.5 mL needed for disposable cuvettes for absorbance scans) are sufficient for the CSF bilirubin determination.³ Preliminary data suggest some negative interference of haemoglobin on CSF bilirubin, which requires further study and quantitation, although it also affects NBA derived by spectrophotometry. For operational purposes, CSF samples are also submitted to spectrophotometry if our analyser haemolytic index is greater than 2.0 mg/dL.

We believe that this methodology should be easily transferable to similar analytical platforms, although it is imperative that each laboratory should meticulously validate its own analytical performance. It offers a robust test and may be particularly useful in peripheral laboratories as a screen to identify those samples that need to be confirmed by spectrophotometry.³

C M Florkowski, S J Southby and P M George

Canterbury Health Laboratories, PO Box 151, Christchurch, New Zealand

	REFERENCES

Top REFERENCES

 

1. Cruickshank A, Auld P, Beetham R et al. Revised national guidelines for analysis of cerebrospinal fluid bilirubin for bilirubin in suspected subarachnoid haemorrhage. Ann Clin Biochem 2008;45:238–44[Abstract/Free Full Text]
2. Chao C-Y, Florkowski CM, Fink JN, Southby SJ, George PM. Prospective validation of cerebrospinal fluid bilirubin in suspected subarachnoid haemorrhage. Ann Clin Biochem 2007;44:140–4[Abstract/Free Full Text]
3. Ungerer JPJ, Southby SJ, Florkowski CM, George PM. Measurement of cerebrospinal fluid bilirubin in suspected subarachnoid hemorrhage. Clin Chem 2004;50:1854–6[Free Full Text]
4. Beetham R. CSF bilirubin-spectrophotometry or direct measurement? Ann Clin Biochem 2007;44:99–100[Free Full Text]

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This Article Full Text (PDF) All Versions of this Article: acb.2008.081101v1 45/6/617    most recent Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Florkowski, C M Articles by George, P M Search for Related Content PubMed PubMed Citation Social Bookmarking                      What's this?