REASSESSMENT OF MICROBIOLOGY PROTOCOL FOR CEREBROSPINAL-FLUID SPECIMENS

Over a 1-year period, 874 cerebrospinal fluid (CSF) specimens from 105 patients were examined by gram-stained smear, culture, and white blood cell count. With these parameters, the efficacy of currently recommended strategies for the detection of organisms in CSF specimens was evaluated. We conclude that all CSF specimens should be cultured on a sheep blood agar plate, a chocolate agar plate, and one tube of thioglycolate broth without indicator regardless of cell count. The sensitivity, specificity, and positive and negative predictive values for a gram-stained smear were 61.9%, 98.9%, 92.9%, and 91.9%, respectively; these same values for white blood cell counts greater than 10/mm3 were 72.0%, 86.4%, 62.1%, and 90.0%, respectively. Gram-positive cocci, particularly staphylococci, were recovered frequently from both true-positive cultures and contaminated cultures. Recovery of the same organism from all media inoculated helped distinguish true-positive from contaminated cultures.