Cytologic interpretation of canine cerebrospinal fluid samples with low total nucleated cell concentration, with and without blood contamination.
BACKGROUND
Cerebrospinal fluid (CSF) is potentially altered by iatrogenic blood contamination at the time of sampling due to the addition of blood-associated leukocytes and protein.


OBJECTIVE
The objective of this study was to assess whether protein concentration, neutrophil percentage, and the presence of activated macrophages, reactive lymphocytes, or eosinophils in CSF samples with low total nucleated cell concentration (TNCC) are affected by blood contamination or associated with central nervous system (CNS) disease.


METHODS
Case records from the Royal Veterinary College Diagnostic Laboratory were searched retrospectively for dogs with CSF having < or =5 TNCC/microL. TNCC, RBC, and protein concentrations; neutrophil percentage; and the presence of activated macrophages, reactive lymphocytes, and eosinophils were recorded. Results of magnetic resonance imaging (MRI) also were recorded as a marker of CNS disease.


RESULTS
Of 906 cases evaluated, 106 (12%) had blood contamination (>500 RBCs/microL) in CSF. Protein concentration and neutrophil percentage were significantly higher and the presence of eosinophils was more likely in blood contaminated vs noncontaminated samples. Non-blood-contaminated samples with activated macrophages or reactive lymphocytes had higher protein concentrations and neutrophil percentages, and those with activated macrophages were more likely to have a positive finding on MRI.


CONCLUSIONS
Protein concentration, neutrophil percentage, and the presence of eosinophils are significantly affected by blood contamination in canine CSF having low TNCC. Activated macrophages and reactive lymphocytes are not affected by blood contamination, however, and may be useful in identifying dogs with CNS abnormalities.
Doyle
Clare
C
Department of Pathology and Infectious Disease, University of London, London, UK. clunniss@rvc.ac.uk
Solano-Gallego
Laia
L
D000818:Animals; D002452:Cell Count / Q000662:veterinary; D002493:Central Nervous System Diseases / Q000134:cerebrospinal fluid / Q000662:veterinary*; D004283:Dog Diseases / Q000134:cerebrospinal fluid*; D004285:Dogs; D004906:Erythrocyte Count / Q000662:veterinary; D007958:Leukocyte Count / Q000662:veterinary; D013048:Specimen Handling / Q000662:veterinary