Test		Number of studies (total patients)	LR+	LR–	Percentage of patients with appendicitis
					Positive test result	Negative test result
Individual blood tests4
Granulocyte count ≥ 13,000 cells per mm3 (13 × 109 per L)		3 (628)	7.1	0.74	88	43
Granulocyte count ≥ 11,000 cells per mm3 (11 × 109 per L)		3 (628)	4.4	0.60	81	38
WBC count ≥ 15,000 cells per mm3 (15 × 109 per L)		14 (3,382)	3.5	0.81	78	45
WBC count ≥ 10,000 cells per mm3 (10 × 109 per L)		14 (3,382)	2.5	0.26	71	21
> 75 percent polymorphonuclear cells		5 (1,067)	2.4	0.24	71	19
CRP > 2 mg per dL (20 mg per L)		9 (1,360)	2.4	0.47	71	32
CRP > 1 mg per dL (10 mg per L)		9 (1,360)	2.0	0.32	67	24
Combination of tests3
Guarding or rebound tenderness and WBC count ≥ 10,000 cells per mm3
	Both abnormal	1 (496)	11.30	—	92	—
	One abnormal	1 (496)	0.94	—	48	—
	None abnormal	1 (496)	0.14	—	12	—
WBC ≥ 10,000 cells per mm3 and CRP > 1.3 mg per dL (12 mg per L)
	Both abnormal	1 (258)	8.2	—	89	—
	One abnormal	1 (258)	1.1	—	52	—
	None abnormal	1 (258)	0.05	—	3	—
WBC ≥ 10,000 cells per mm3, CRP > 0.8 mg per dL (8 mg per L), and IL-6 > 60 ng per L (60 mcg per L)
	All abnormal	1 (102)	17.00	—	94	—
	Any one or two abnormal	1 (102)	2.06	—	67	—
	None abnormal	1 (102)	0.03	—	3	—
Imaging studies4
CT (children)		8 (2,506)	18.8	0.06	95	6
CT (adults)		21 (3,438)	15.7	0.06	94	6
Ultrasonography (children)		23 (8,758)	14.7	0.13	94	11
Ultrasonography (adults)		15 (1,947)	11.9	0.18	92	15