TABLE 1.

Factors That Predict the Absence of Meningitis

Sensitivity (95% CI)Specificity (95% CI)Positive Predictive Value (95% CI)Negative Predictive Value (95% CI)
O:P ratio ≤ 0.0191.1% (79–98)100% (74–100)100% (91–100)75% (48–93)
O:P ratio ≤ 197.8% (88–100)58.3% (28–85)89.8% (78–97)87.5% (47–100)
WBC:RBC ratio ≤ 1:100 (0.01)84.4% (70–94)100% (78–100)100% (92–100)63.2% (38–84)
WBC:RBC ratio ≤ 1:500 (0.002)51.1% (36–66)100% (78–100)100% (88–100)35.3% (20–54)
Absence of pleocytosis (<5 WBC)33.3% (20–49)100% (74–100)100% (78–100)28.6% (16–45)
No PMN predominance (<50% PMNs)72.5% (56–85)90.9% (59–100)96.7% (83–100)47.6% (26–70)
Gram-stain negative100% (92–100)75% (43–95)93.5% (82–99)100% (66–100)
Normal CSF protein (<40)80% (65–90)0 (0–28)76.6% (62–88)0 (0–34)
Normal CSF glucose (>40)95.6% (85–99)83.3% (52–98)95.6% (85–99)83.3% (52–98)