Interpretation of Cerebrospinal Fluid Analysis from Recumbent Cows Using Different Thresholds of Red Blood Cell Count

Background: Hemodilution of the cerebrospinal fluid (CSF) could confound interpretation of results. Accurately predicting total nucleated cells count (TNCC) and total protein concentration (TPC) attributable to hemodilution is difficult.

Objective: To determine the effects of hemodilution on TPC and TNCC in bovine CSF.

Methods: Retrospective review of CSF analysis results of downer dairy cows treated at Centre hospitalier universitaire vétérinaire between January 2006 and December 2014. Descriptive statistics were performed using 3 scenarios.

Results: Among the 235 samples included, red blood cell (RBC) count (RBCC) ranged from 0 to 869 220 RBC/μL (median = 6.6), TPC ranged from 0.04 to 6.51 g/L (median = 0.27), and TNCC ranged from 0 to 7500 cell/μL (median = 1.1). Among the 157 samples that had <30 RBC/μL (a threshold used in other species), TPC and TNCC varied between 0.13 and 1.06 g/L (median = 0.27) and between 0 and 31.4 cell/μL (median = 0.6), respectively. Eighty-four samples had TPC <0.25 g/L and TNCC ≤4.5 cell/μL. Among those 84 samples, RBCC varied between 0 and 1290 RBC/μL (median = 4.7). In 20 samples, TNCC was 0 with a variation in RBCC between 0 and 840 RBC/μL (median = 3.9). No strong correlations between RBCC and TNCC and TPC were found.

Conclusions: A cutoff around 200 RBC/μL is proposed as clinically meaninful in bovine CSF. Results between 200 and 1290 RBC/μL are equivocal.