Retrospective analysis: are fever and altered mental status indications for lumbar puncture in a hospitalized patient who has not undergone neurosurgery?

Although nosocomial meningitis is rare in nonsurgical patients, lumbar punctures are frequently performed on hospitalized medical patients who develop delirium and/or fever. A retrospective review was undertaken to determine the yield of lumbar puncture in this setting and to compare it with the yield for suspected community-acquired meningitis. Of 232 lumbar punctures studied, 51 (22%) were performed to rule out nosocomial meningitis, while 181 (78%) were done to rule out community-acquired meningitis. No lumbar puncture performed for suspected nosocomial meningitis was positive, while results of 26 (14%) of those done for suspected community-acquired meningitis were abnormal (P < .01). Patients whose lumbar punctures were positive more often had headache or meningeal signs than those whose lumbar punctures were negative, and only 11 patients (22%) who had lumbar punctures performed for suspected nosocomial meningitis had headache or meningeal signs. We conclude that lumbar punctures performed for suspected nosocomial meningitis in nonsurgical patients have a low yield and that in some low-risk patients without headache or meningeal signs, lumbar puncture may be unnecessary.