Table 2.

Utility of unadjusted and adjusted white blood cell values to predict meningitis.

Predictor	RBCs in CSF (/mm3)	Cut-off*	Sensitivity (%)	Specificity (%)	+ LR	− LR
WBC, unadjusted	<500	WBC ≥ 10	70	77	3.0	0.39
		WBC ≥ 20	61	90	6.3	0.43
		WBC ≥ 100	44	98	25.0	0.57
WBC, unadjusted	≥500	WBC ≥ 10	86	42	1.5	0.34
		WBC ≥ 20	82	57	1.9	0.31
		WBC ≥ 100	64	82	3.5	0.44
WBC, adjusted by 500:1 ratio	≥500	WBC ≥ 10	82	67	2.5	0.27
		WBC ≥ 20	74	75	3.0	0.35
		WBC ≥ 100	56	89	5.2	0.49
WBC, adjusted by 1000:1 ratio	≥500	WBC ≥ 10	82	58	2.0	0.31
		WBC ≥ 20	76	69	2.4	0.35
		WBC ≥ 100	58	86	4.3	0.49
WBCobserved − WBCpredicted	≥500	WBC ≥ 10	75	75	3.0	0.33
		WBC ≥ 20	73	82	4.0	0.33
		WBC ≥ 100	55	92	6.8	0.49
Observed:predicted ratio	≥500	O:P ≥ 1	75	55	1.7	0.45
		O:P ≥ 10	57	93	7.6	0.47
		O:P ≥ 100	36	99	42.3	0.64

LR (likelihood ratio).