Stability of cerebrospinal fluid/serum glucose ratio and cerebrospinal fluid lactate concentrations over 24 h: analysis of repeated measurements.
BACKGROUND
The cerebrospinal fluid/serum glucose ratio (CSF/S(glu)) and CSF lactate measurements are part of the routine CSF work-up. The in-vitro stability of both metabolites in CSF has not been formally investigated.


METHODS
Following collection, CSF/S(glu) and CSF L-lactate concentrations were measured repeatedly at five time points (baseline, 1 h, 2 h, 4 h and 24 h) in CSF and whole blood specimens stored at 4 degrees C.


RESULTS
CSF glucose and lactate concentrations were stable over 24 h in samples with both normal and increased CSF cell counts. The CSF cell count did not influence CSF glucose concentrations, but correlated significantly with CSF lactate concentrations. The CSF/S(glu) increased significantly over time due to glucose consumption.


CONCLUSIONS
Glucose and L-lactate are stable in CSF specimens at 4 degrees C over 24 h. The CSF/S(glu) seems to be more reliable than CSF lactate because it is independent of the cell count. Falsely increased CSF/S(glu) may be corrected by the rate of consumption of blood glucose.
Dujmovic
Irena
I
Department of Neurology, Innsbruck Medical University, Innsbruck, Austria.
Deisenhammer
Florian
F
D015415:Biomarkers / Q000097:blood / Q000134:cerebrospinal fluid; D001786:Blood Glucose / Q000378:metabolism*; D003080:Cold Temperature; D005947:Glucose / Q000032:analysis / Q000134:cerebrospinal fluid*; D006801:Humans; D019344:Lactic Acid / Q000134:cerebrospinal fluid*; D015203:Reproducibility of Results; D013048:Specimen Handling / Q000379:methods / Q000592:standards; D013997:Time Factors
D015415:Biomarkers; D001786:Blood Glucose; D019344:Lactic Acid; D005947:Glucose