Effects of Blood Contamination on Total Nucleated Cell Counts and Protein Concentrations in Bovine CSF

Analysis of cerebrospinal fluid (CSF) is a useful procedure for determining a diagnosis and prognosis in neurologic patients. Blood contamination during CSF sampling may confound interpretation of results since total nucleated cells count (TNCC) and total protein concentration (TPC) could be falsely elevated. Accurately predicting TNCC and TPC attributable to blood contamination is difficult.

The objective was to determine the effects of blood contamination on bovine CSF TNCC and TPC using samples spiked with known dilutions of whole blood.

Cerebrospinal fluid was collected from the lumbosacral subarachnoid space in 9 clinically normal cows. For each cow, 1μL (5.76-6.92x10⁶RBC) of her own blood was added to 999μL of her CSF (sample A). Next, sample A was diluted 1:2, 1:5, 1:10, 1:100 and 1:1000 (sample B to F, respectively) using CSF from the same animal (0-1050 RBC/μL). TNCC and TPC were measured for all samples (prior and after adding blood). Repeated measures ANOVA were used to assess whether there was a difference in TNCC and PC at each dilution.

Overall, there was a significant association between the amount of blood added and the TNCC and TPC obtained values (P<0.01). A significant difference on TNCC and TPC was observed (P<0.01) between CSF before addition of blood and the samples A and B. On samples C to F, TNCC and TPC were not significantly different from original sample values.

While blood contamination appears to impact the TNCC and TPC, up to 3350 RBC/μL are necessary to measure a significant difference according to this experimental design.