Lysis of erythrocytes and leukocytes in traumatic lumbar punctures.

We created "bloody taps" by adding homologous blood to acellular samples of CSF and counted the RBCs and WBCs at specific time intervals. After two hours at room temperature (22 degrees C), 40% of the WBCs in the traumatic tap had lysed. At 4 degrees C, 15% of the cells lysed in the same period of time. After five hours at 22 degrees C, 53% of the WBCs had lysed, while refrigeration reduced this figure to 31%. The clinical implications of these data are clear. If a sample of CSF is not promptly refrigerated and analyzed, WBC lysis will result in a false impression of the number of WBCs that are present. This lysis of WBCs reduces the reliability of the corrective formula that uses CSF and blood RBC and WBC counts to estimate the number of WBCs in CSF that are attributable to contamination with blood.