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Volume 15, Number 8—August 2009

Research

Reproducibility of Serologic Assays for Influenza Virus A (H5N1)

Iain StephensonComments to Author , Alan Heath, Diane Major, Robert W. Newman, Katja Hoschler, Wang Junzi, Jacqueline M. Katz, Jerry P. Weir, Maria C. Zambon, and John M. Wood
Author affiliations: University of Leicester, Leicester, UK (I. Stephenson); National Institute for Biological Standards and Controls, Potters Bar, UK (A. Heath, D. Major, R.W. Newman, J.M. Wood); Health Protection Agency, Colindale, UK (K. Hoschler, M.C. Zambon); Centers for Disease Control and Prevention, Atlanta, Georgia, USA (J.M. Katz); Food and Drug Administration, Rockville, Maryland, USA (J.P. Weir); National Institute for the Control of Pharmaceutical and Biological Products, Beijing, People’s Republic of China (W. Junzhi)

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Table 1

Geometric mean titers (reciprocal shown) and geometric coefficient of variation for the candidate antibody standard 07/150, measured by each participating laboratory for each influenza virus*

Laboratory no. Assay tested and virus used (phylogenetic clade)
hHI†
Neutralization†
NIBRG-14‡§ clade 1 NIBRG-23‡ clade 2.2 IBCDC-RG5§ clade 2.3 NIBRG-14‡§ clade 1 NIBRG-23‡ clade 2.2 IBCDC-RG5§ clade 2.3
1 101 160 80 480 605 419
2 25 25 101 1016 640 806
3 403 320 160 1810 1810 226
4 160 80 80 336 233 469
5 406 256 256 450 270 632
6 80 160 202 320 320 202
7 101 63 63 127 101 80
8 160 80 80 320 160 160
9 160 183 115 160 52 80
10 160 80 105 960 210 733
11¶ ND ND ND 640 254 320
12 403 160 202 320 160 160
13 80 32 25 640 320 320
14 160 127 25 2032 905 508
15
101
63
63

731
313
471
Overall GMT 140 102 91 518 291 299
GCV, % 112 109 101 120 140 109

*GMT. geometric mean titer; GCV, geometric coefficient of variation; hHI, hemagglutination-inhibition assay using horse erythrocytes; neutralization, virus neutralization assay; ND, not done.
†GMT neutralization vs. hHI (NIBRG-14, p = 0.003; NIBRG-23, p = 0.005; IBCDC-RG5, p = 0.005 by Wilcoxon signed-rank test).
‡GMT NIBRG-14 vs. NIBRG-23 (hHI, p = 0.039; neutralization, p = 0.004 by Wilcoxon signed-rank test).
§GMT NIBRG-14 vs. IBCDC-RG5 (hHI, p = 0.028; neutralization, p = 0.008 by Wilcoxon signed-rank test).
¶Laboratory 11 did not return hHI data.

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