Test		Population	Positive likelihood ratio	Negative likelihood ratio	Negative predictive value (prevalence of 33%)*	Negative predictive value (prevalence of 50%)*
White blood cell count16		Adults and children with suspected appendicitis (meta-analysis of 14 studies; studies with children only excluded)
	≥ 10,000 per μL (10.0 × 109 per L)		2.5	0.26	12%	21%
	≥ 12,000 per μL (12.0 × 109 per L)		2.8	0.48	19%	32%
	≥ 14,000 per μL (14.0 × 109 per L)		3.0	0.69	26%	41%
C-reactive protein level16		Adults and children with suspected appendicitis (meta-analysis of 14 studies; studies with children only excluded)
	> 10 mg per L (95.24 nmol per L)		2.0	0.32	14%	24%
	> 20 mg per L (190.48 nmol per L)		2.4	0.47	19%	32%
APPY1 biomarker panel17		Adults with suspected appendicitis (n = 422)	1.5	0.07	3%	7%
APPY1 biomarker panel5		Children with suspected appendicitis (n = 185)	1.7	0.06	3%	6%
APPY1 biomarker panel plus absolute neutrophils < 7,500 per μL (7.5 × 109 per L)5		Children with suspected appendicitis (n = 185)	1.6	0.01	1%	1%