Differences in total protein concentration, nucleated cell count, and red blood cell count among sequential samples of cerebrospinal fluid from horses

Objective-To examine total protein concentration and cell counts of sequent ially collected samples of CSF to determine whether blood contamination dec reases in subsequent samples and whether formulas used to correct nucleated cell count and total protein concentration are accurate. Design-Case series. Animals-22 horses. Procedure-For each horse, 3 or 4 sequential 2-ml samples of CSF were collec ted from the subarachnoid space in the lumbosacral region into separate syr inges, and blood was obtained from the jugular vein. Total protein concentr ation, nucleated cell count, and RBC counts were determined in ail samples. Results-Among 3 sequential samples, total protein concentration and RBC cou nt were significantly lower in samples 2 and 3, compared with sample 1. Nuc leated cell count was significantly tower in sample 3, compared with sample 1. Among 4 sequential samples, total protein concentration and RBC count w ere significantly lower in samples 2, 3, and 4, compared with sample 1. Nuc leated cell count was significantly lower in samples 3 and 4, compared with sample 1. For 3 correction formulas, significant differences in corrected values for nucleated cell count and total protein concentration were detect ed between sample 1 and sample 3 or 4. Conclusions and Clinical Relevance-Because iatrogenic blood contamination d ecreases in sequential CSF samples, a minimum of 3 samples should be collec ted before submitting the final sample for analysis, Formulas to correct nu cleated cell count and total protein concentration are inaccurate and shoul d not be used to correct for blood contamination in CSF samples.