Document Detail

An improved laboratory protocol to assess subarachnoid haemorrhage in patients with negative cranial CT scan.
MedLine Citation:
PMID:  16879058     Owner:  NLM     Status:  MEDLINE    
BACKGROUND: The laboratory analysis of cerebrospinal fluid (CSF) plays a key role in considering subarachnoid haemorrhage (SAH) in patients with clinical suspicion, but negative CT scan. Although the determination of the CSF bilirubin concentration generally provides high sensitivity, it was recently shown that specificity and positive predictive value are unacceptably low, limiting its use as a diagnostic tool. METHODS: We intended to design and evaluate an improved laboratory protocol, which fulfills the requirement of better specificity without losing sensitivity. We present a procedure in which a "bili-excess" concentration is determined, which is the surplus CSF bilirubin measured after subtraction of an estimated upper limit for the individual patient. The latter is calculated from [bilirubin](serum), [albumin](serum) and [albumin](CSF), taking into account the propagation of analytical errors in the individual analyses. We investigated the applicability of direct absorption vs. derivative spectroscopy, thereby addressing the influence of various calibration methods. We evaluated our procedure in 92 CSF samples drawn from patients with (n=37) and without (n=55) clinical suspicion of SAH. RESULTS: In our study population, we show that specificity increases from 0.83 (95% CI, 0.74-0.91) to 1.00 (95% CI, 0.96-1.00) using the bili-excess concept, with an established upper limit for bili-excess of 0.11 micromol/L instead of the recommended use of an "uncorrected" CSF bilirubin upper limit of 0.20 micromol/L. Sensitivity in both cases is 1.00 (95% CI, 0.66-1.00). We demonstrate the merit of allowing for analytical imprecision in the bili-excess concept. CONCLUSIONS: We provide a quantitative procedure to explore the likelihood of (CT-negative) SAH independent of the absolute CSF bilirubin concentration by considering the "bili-excess" concentration per individual, using derivative spectroscopy to determine CSF bilirubin. This procedure led to an increase in specificity to 1.00 (95% CI, 0.96-1.00) in our study population.
Joke J Apperloo; Fedde van der Graaf; Paul L I Dellemijn; Huib L Vader
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Publication Detail:
Type:  Comparative Study; Journal Article    
Journal Detail:
Title:  Clinical chemistry and laboratory medicine : CCLM / FESCC     Volume:  44     ISSN:  1434-6621     ISO Abbreviation:  Clin. Chem. Lab. Med.     Publication Date:  2006  
Date Detail:
Created Date:  2006-08-01     Completed Date:  2006-10-26     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  9806306     Medline TA:  Clin Chem Lab Med     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  938-48     Citation Subset:  IM    
Laboratory of Clinical Chemistry, Máxima Medical Centre, Veldhoven, The Netherlands.
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MeSH Terms
Bilirubin / cerebrospinal fluid
Cerebrospinal Fluid / chemistry*
Diagnosis, Differential
Methemoglobin / cerebrospinal fluid
Oxyhemoglobins / cerebrospinal fluid
Subarachnoid Hemorrhage / cerebrospinal fluid,  diagnosis*
Tomography, X-Ray Computed / methods*
Reg. No./Substance:
0/Oxyhemoglobins; 635-65-4/Bilirubin; 9008-37-1/Methemoglobin

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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