TABLE 2.

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

DrugVirusIC50 (nM) per seasonTotal IC50 (nM)aP valueb
2004-20052005-20062006-2007
Range (n)Mean ± SDRange (n)Mean ± SDRange (n)Mean ± SDRange (n)Mean ± SDCutoffStatistical cutoff
OseltamivirA(H1N1)0.35-6.05 (53)0.96 ± 0.970.19-10.00 (258)1.15 ± 1.010.16-4.51 (817)0.84 ± 0.450.16-10.00 (1,128)0.91 ± 0.662.892.43<0.0001
A(H3N2)0.11-3.45 (142)0.52 ± 0.340.08-3.05 (186)0.59 ± 0.460.04-5.16 (908)0.40 ± 0.320.04-5.16 (1,236)0.44 ± 0.351.501.51<0.0001
B1.24-11.63 (175)3.23 ± 1.630.70-7.95 (203)3.45 ± 1.360.19-10.48 (511)3.47 ± 1.240.19-11.63 (889)3.42 ± 1.357.478.640.122
ZanamivirA(H1N1)0.50-6.48 (53)1.12 ± 0.880.20-13.50 (259)1.30 ± 1.340.06-11.60 (822)0.98 ± 0.740.06-13.50 (1,134)1.06 ± 0.933.853.32<0.0001
A(H3N2)0.49-13.98 (140)3.66 ± 2.510.14-11.77 (186)2.62 ± 2.040.15-20.00 (907)2.35 ± 2.160.14-20.00 (1,233)2.54 ± 2.229.209.93<0.0001
B1.12-16.51 (175)4.21 ± 2.650.85-17.86 (203)4.84 ± 2.770.35-12.00 (511)3.36 ± 2.140.35-17.86 (889)3.87 ± 2.4711.2914.21<0.0001
  • a A 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 >X0.75 + 3 IQR.

  • b P value was determined by analysis of variance (where α = 0.05).