Abstract
OBJECTIVES: To identify indicators of false pleocytosis in adults with traumatic lumbar puncture (LP), and determine specificities and sensitivities of commonly used CSF correction factors. METHODS: Adults who underwent 4-tube CSF collection were reviewed. Study inclusion required elevated tube 1 red blood cell (RBC) count, tube 1 pleocytosis, and normalized tube 4 RBC count. Tube 4 white blood cell (WBC) count served as the reference standard. Specificities and sensitivities of 3 correction factors (1 WBC:500 RBC, 1 WBC:1000 RBC, and 1 WBC:1500 RBC) were calculated. RESULTS: One hundred ninety-five adults were included. Among them, 106 (54%) had false tube 1 pleocytosis; these patients had a significantly higher median CSF RBC count and lower median CSF WBC count than those with true tube 1 pleocytosis. Specificities and sensitivities of correction factors ranged from 71.7% to 29.2% and 84.3% to 97.8%, respectively; 1 WBC:500 RBC had highest specificity for pleocytosis, while 1 WBC:1500 RBC had highest sensitivity. Irrespective of correction factor used, false-positive and false-negative determinations of pleocytosis were usually mild (≤20 WBCs/μL). DISCUSSION: Indicators of false pleocytosis in adults with traumatic LP include bloodier CSF and milder pleocytosis, suggesting that correction factors are most useful in such cases. Across correction factors, an expected specificity/sensitivity tradeoff is observed. Corrected CSF WBC counts suggesting only mild pleocytosis should be interpreted cautiously.