TABLE 2.

NAI data analysis of IC₅₀s grouped according to season and virus type/subtype

Drug	Virus	IC50 (nM) per season						Total IC50 (nM)a				P valueb
		2004-2005		2005-2006		2006-2007
		Range (n)	Mean ± SD	Range (n)	Mean ± SD	Range (n)	Mean ± SD	Range (n)	Mean ± SD	Cutoff	Statistical cutoff
Oseltamivir	A(H1N1)	0.35-6.05 (53)	0.96 ± 0.97	0.19-10.00 (258)	1.15 ± 1.01	0.16-4.51 (817)	0.84 ± 0.45	0.16-10.00 (1,128)	0.91 ± 0.66	2.89	2.43	<0.0001
	A(H3N2)	0.11-3.45 (142)	0.52 ± 0.34	0.08-3.05 (186)	0.59 ± 0.46	0.04-5.16 (908)	0.40 ± 0.32	0.04-5.16 (1,236)	0.44 ± 0.35	1.50	1.51	<0.0001
	B	1.24-11.63 (175)	3.23 ± 1.63	0.70-7.95 (203)	3.45 ± 1.36	0.19-10.48 (511)	3.47 ± 1.24	0.19-11.63 (889)	3.42 ± 1.35	7.47	8.64	0.122
Zanamivir	A(H1N1)	0.50-6.48 (53)	1.12 ± 0.88	0.20-13.50 (259)	1.30 ± 1.34	0.06-11.60 (822)	0.98 ± 0.74	0.06-13.50 (1,134)	1.06 ± 0.93	3.85	3.32	<0.0001
	A(H3N2)	0.49-13.98 (140)	3.66 ± 2.51	0.14-11.77 (186)	2.62 ± 2.04	0.15-20.00 (907)	2.35 ± 2.16	0.14-20.00 (1,233)	2.54 ± 2.22	9.20	9.93	<0.0001
	B	1.12-16.51 (175)	4.21 ± 2.65	0.85-17.86 (203)	4.84 ± 2.77	0.35-12.00 (511)	3.36 ± 2.14	0.35-17.86 (889)	3.87 ± 2.47	11.29	14.21	<0.0001

^aA total of 3,261 isolates were tested(12 extreme outliers were excluded from the statistical analysis for the respective drug eliciting the outlier IC₅₀s). The cutoff value was determined based on the elected criterion of the mean IC₅₀ value + 3 standard deviations (SD). The statistical cutoff value was determined based on the IC₅₀ value of >X_0.75 + 3 IQR.

^bP value was determined by analysis of variance (where α = 0.05).