Table 5. Performance of case definitions in the comparison between GrippeNet.fr incidence estimates and official estimates, France, 2012/13 and 2013/14.

Comparison	ILI and ARI case definitions	2012/13			2013/14
		Correlation r (95% CI)	Error e	Peak week differencea	Correlation r (95% CI)	Error e	Peak week differencea
GN ILI vs sentinel ILI	GNILI vs RS	0.89 (0.75–0.96)	0.62	2	0.84 (0.64–0.94)	0.51	0
	GNILIf vs RS	0.81 (0.58–0.92)	0.56	-1	0.83 (0.61–0.93)	1.40	-1
	GNILI– vs RS	0.95 (0.87–0.98)	1.04	-1	0.91 (0.79–0.97)	2.35	-1
	GNILI–f vs RS	0.94 (0.86–0.98)	2.06	0	0.83 (0.62–0.93)	4.58	-1
GN ARI vs sentinel ARI	GNARI vs GROG	0.91 (0.79–0.96)	0.20	-1	0.93 (0.82–0.97)	0.18	-1
	GNARI +  vs GROG	0.90 (0.78–0.96)	0.30	0	0.90 (0.76–0.96)	0.31	-1
	GNECDC vs GROG	0.96 (0.89–0.98)	0.13	0	0.93 (0.83–0.97)	0.16	-1
GN ILI vs sentinel ARI	GNILI vs GROG	0.77 (0.51–0.90)	0.95	2	0.84 (0.64–0.94)	0.94	0
	GNILIf vs GROG	0.82 (0.61–0.93)	0.87	-1	0.86 (0.68–0.94)	0.87	-1
	GNILI– vs GROG	0.81 (0.59–0.92)	0.77	-1	0.86 (0.68–0.95)	0.80	-1
	GNILI–f vs GROG	0.88 (0.73–0.95)	0.63	0	0.89 (0.73–0.95)	0.67	-1
GN ARI vs sentinel ILI	GNARI vs RS	0.76 (0.49–0.90)	7.9	-1	0.66 (0.31–0.85)	17.5	-1
	GNARI +  vs RS	0.76 (0.49–0.90)	8.7	0	0.60 (0.21–0.82)	19.7	-1
	GNECDC vs RS	0.85 (0.66–0.94)	7.4	0	0.66 (0.31–0.85)	17.0	-1

ARI: acute respiratory infection; CI: confidence interval; GN: GrippeNet.fr; GROG: regional influenza surveillance group estimating the weekly number of ARI cases; ILI: influenza-like illness; RS: sentinel network estimating the weekly number of ILI cases.

The different case definitions used in GN (GN_ILI, GN_ILIf, GN_ILI-, GN_ILI-f, GN_ARI, GN_ARI +, GN_ECDC) are described in Table 1.

^a The difference is calculated as peak week of GN incidence minus peak week of official estimate.