Distinguishing cerebrospinal fluid abnormalities in children with bacterial meningitis and traumatic lumbar puncture

The characteristics of cerebrospinal fluid (CSF) associated with traumatic lumbar puncture, defined as CSF red blood cell (RBC) count >1000/mm³, were reviewed in 92 previously healthy children >1 month of age; 30 had bacterial meningitis and 62 had negative CSF cultures. The purpose was to distinguish CSF profiles of the two groups despite contamination with peripheral blood elements. In each case, white blood cell (WBC) counts were observed (0) and compared with those predicted (P), calculated as P = CSF RBC A- (blood WBC/blood RBC). Comparison ofO:P ratios revealed that all 30 patients with bacterial meningitis had ratios, 28 (93%) had ratios >10, and 24 (80%) had ratios >100; by contrast, only 2 patients (3%) with culture-negative CSF had ratios >10, 21 (34%) had ratios of 110, and 39 (63%) had ratios <1. Significant differences were observed in the rate of O:P ratio (100% vs. 32%), CSF differential cell count predominance of polymorphonuclear leukocytes (97% vs. 11%), hypoglycorrhachia (73% vs. 3%), and positive Gram's-stained smear for pathologic organisms (80% vs. 0) in those with and without bacterial meningitis, respectively (P <.0001).Thus, in children >1 month of age, CSF abnormalities associated with bacterial meningitis are rarely obscured by blood contamination from traumatic lumbar puncture.