Influence of artificial blood contamination of the analysis of cerebrospinal fluid.

The influence of artificial blood contamination on the quantitative values obtained in the routine examination of the CSF was investigated. On the basis of dilution series from CSF and blood, the correlation between the number of added erythrocytes and the results of leukocyte counts, protein, glucose and IgG estimation was studied. In addition, the influence of the time between CSF sampling and investigation on erythrocytes and leukocytes, IgG, glucose, pH value and ammonia content in CSF contaminated with blood was investigated. The following data relevant to routine examinations resulted: there are linear correlations between the number of erythrocytes artificially added to the CSF and the leukocyte count, the total protein and the IgG content, whereas glucose is unaffected by the artificial admixture of blood. With regard to the time between sampling and investigation of the CSF, it was shown that the IgG values in blood-contaminated and blood-free CSF do not change. A correct IgG estimation is hence possible even several days after lumbar puncture. The cell count decreases exponentially with time, whereas the total protein rises with progressive cytolysis. The glucose values decrease both in native and in artificially blood-contaminated CSF, whereas the pH values rise rapidly, evidently due to release of ammonia and primary amines from the proteins and amino acids present in the CSF.