Interpretation of traumatic lumbar puncture. Predictive value in the presence of meningitis.

Contamination of cerebrospinal fluid (CSF) with blood was studied prospectively in nine children with aseptic meningitis as the second phase of a study reported in this volume last month. Using criteria defined in the first phase, four of nine patients had recognizably abnormal CSF after experimental contamination with blood. As a third phase of the study, 53 children with bacterial meningitis were reviewed retrospectively to assess if hypothetical contamination of CSF with blood would have disguised their abnormal CSF studies. All but one of these 53 patients had either an abnormal CSF glucose or a positive gram stain (indicators independent of contamination with blood), and none would have gone undiagnosed with hypothetical contamination of up to 200,000 red cells per cubic millimeter. Guidelines for interpretation of laboratory studies following traumatic lumbar puncture are reviewed.