Emergency department lumbar puncture: clinical application and utility of laboratory testing.

Lumbar puncture is an emergency department procedure for evaluating patients with suspected central nervous system infection or hemorrhage. To determine whether extensive testing of cerebrospinal fluid (CSF) obtained from emergency department patients was useful, charts of 104 adult patients who underwent lumbar puncture in a university hospital emergency department were reviewed. Examination of the CSF disclosed pleocytosis in 25 (24%) of the patients; the presence of red blood cells was considered to be clinically significant in two patients. An abnormal level of CSF protein was present in 62% of patients, and abnormal levels of glucose in 32%. Fungal element testing was negative each of the 72 times it was performed; Gram stain disclosed a bacterial pathogen in one patient. Cultures for fungus and tuberculosis were uniformly negative, as were all immunologic tests. Bacterial cultures grew a pathogen in one patient. No patient with a normal neurologic examination and normal initial CSF analysis was diagnosed subsequently as having acute central nervous system disease. The preponderance of negative or normal results of testing of CSF suggests that extensive testing may not be necessary for all patients. Limitation of sophisticated testing to only those samples with abnormal cell counts or chemistries or from patients at high risk should result in substantial cost saving without compromising patient care.