Table 3.

Performance in outbreak detection according to patient criterion and a variety of upper control limits defined by 1 standard deviation and 85% confidence interval, with and without clustering.

	Without clustering	With clustering (d=1)g	With clustering (d=0)
	1 standard deviation	1 standard deviation	Upper 85% CI
Sensitivity (%)a	86.7 (26/30)	86.7 (26/30)	90.0 (27/30)
Specificity (%)b	83.5 (626/750)	83.2 (624/750)	83.6 (627/750)
PPV (%)c	17.3 (26/150)	17.1 (26/152)	18.0 (27/150)
NPV (%)d	99.4 (626/630)	99.4 (624/628)	99.5 (627/630)
AUCe (95% CIf)	0.85 (0.78-0.92)	0.85 (0.78-0.92)	0.87 (0.80-0.93)

^a-g as shown in Table 2 footnotes.