Table 3.

Discriminatory performance of WBC, CRP, PCT and the constructed model for detecting patients with H1N1 influenza and a bacterial co‐infection

Variables	AUC (95% CI)	Cutoff level	Sensitivity	Specificity	PPV	NPV
WBC	0.551 (0.502‐0.592)	11.56	0.267	0.887	0.144	0.910
CRP	0.762 (0.722‐0.803)	13.55	0.633	0.856	0.330	0.971
PCT	0.801 (0.772‐0.855)	0.52	0.643	0.886	0.773	0.852
PCT&CRP*	0.893 (0.852‐0.934)	‐	0.830	0.868	0.854	0.846

AUC, area under the receiver operating characteristic curve; CI, confidence interval; CRP, C‐reactive protein; NPV, negative predictive value; PCT, procalcitonin; PPV, positive predictive value; WBC, white blood cell. *PCT&CRP: Logit (P) = −1.912 + 0.546 PCT + 0.087 CRP.