Effects of time, initial composition, and stabilizing agents on the results of canine cerebrospinal fluid analysis.
BACKGROUND
Cerebrospinal fluid (CSF) is considered highly labile, but not all samples are analyzed immediately. Changes in the composition of CSF could potentially affect diagnostic test results and thus influence decisions about patient management. There has been little scientific inquiry into how variables such as time, initial composition, and storage conditions affect results of standard laboratory analysis of CSF.


OBJECTIVE
The objectives of this study were to determine the effects of time, protein concentration, and presence or absence of exogenous stabilizing agents on standard CSF analysis results.


METHODS
Thirty abnormal CSF samples from 26 dogs were evaluated. Samples were divided into aliquots comprising different treatment groups and stored at 4 degrees C. Total nucleated cell count (TNCC), differential cell count (DCC), and cell morphology were evaluated for all groups; protein concentration was measured for selected groups. Unaltered aliquots were analyzed immediately (T0Hr) and at 2, 4, 8, 12, 24, and 48 hours (T2Hr-T48Hr); aliquots with added fetal calf serum (FCS) or hydroxyethyl starch (hetastarch) were analyzed at T48Hr.


RESULTS
Significant time-dependent changes were observed in DCC in unaltered samples. Mononuclear cells deteriorated more rapidly than did neutrophils. Based on microscopic examination and subjective scoring of cell morphology, cells were consistently more degenerate by T24Hr compared with T0Hr. Samples with protein concentrations > or =50 mg/dL were less susceptible to cell deterioration than those with lower protein concentrations. Adding either FCS or hetastarch improved sample stability.


CONCLUSIONS
Delayed analysis of canine CSF by 4-8 hours is unlikely to alter diagnostic interpretation, especially for samples with protein concentrations > or =50 mg/dL. The likelihood of misinterpretation is higher for samples with low cellularity or low protein concentration. We provide specific recommendations for adding FCS or hetastarch to samples that will not be analyzed within 1 hour.
Fry
Michael M
MM
Department of Pathology, School of Veterinary Medicine, University of California-Davis, Davis, CA, USA. mfry@utk.edu
Vernau
William
W
Kass
Philip H
PH
Vernau
Karen M
KM
D000818:Animals; D002452:Cell Count / Q000662:veterinary; D002555:Cerebrospinal Fluid / Q000737:chemistry*; D003951:Diagnostic Errors / Q000662:veterinary; D003955:Diagnostic Tests, Routine / Q000379:methods / Q000662:veterinary*; D004285:Dogs; D013048:Specimen Handling / Q000379:methods / Q000662:veterinary*; D013997:Time Factors