Interpretation of traumatic lumbar puncture. A prospective experimental model.

Contamination of cerebrospinal fluid (CSF) with blood at the time of collection interferes with the interpretation of laboratory studies. Twenty-four children with normal CSF were studied prospectively using an experimental model. Blood was added to clear CSF, producing red cell counts from 1,000 to 600,000 cells per cubic millimeter. The expected values for white blood cell count, protein, percent neutrophils, and glucose were calculated, using the results from uncontaminated CSF, peripheral blood cell counts, blood protein, and the red blood cell count of the contaminated specimen. The ratio of observed values to expected values ranged from 0.13 to 3.00 for CSF white blood cell count (mean 0.96, standard deviation 0.56), from 0.55 to 1.63 for CSF protein (mean 0.97, standard deviation 0.23), and from 0.10 to 2.25 for percent neutrophils in the CSF (mean 1.17, standard deviation 0.41). CSF glucose was unchanged by the addition of blood. Guidelines for interpretation of laboratory studies following traumatic lumbar puncture are suggested.