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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 3

Interlaboratory geometric coefficients of variation of absolute titers and titers and relative to candidate antibody standard 07/150 and sheep serum summarized over all serum for each influenza virus tested by hHI and neutralization*

%GCV, virus strain hHI, all serum samples, median (min–max) Neutralization, all serum samples, median (min–max)
%GCV of absolute titer
A/Vietnam/1194/NIBRG-14 clade 1 125 (31–582)† 175 (86–232)†
A/Turkey/23/NIBRG-23 clade 2.2 114 (29496) 170 (101283)
A/Anhui/IBCDC-RG5 clade 2.3
108 (22487)
112 (68147)
%GCV of titers relative to 07/150
A/Vietnam/1194/NIBRG-14 clade 1 61 (34–535) 77 (37–285)
A/Turkey/23/NIBRG-23 clade 2.2 106 (18487) 144 (33309)
A/Anhui/IBCDC-RG5 clade 2.3
105 (0545)
196 (41298)
%GCV of titers relative to serum P
A/Vietnam/1194/NIBRG-14 clade 1 796 (39–1,020) 249 (162–381)
A/Turkey/23/NIBRG-23 clade 2.2 689 (7953) 237 (90844)
A/Anhui/IBCDC-RG5 clade 2.3 752 (01,005) 195 (66263)
A/Vietnam/1194/NIBRG-14 clade 1 (excluding laboratory 5) 68 (32–174) 255 (162–396)
A/Turkey/23/NIBRG-23 clade 2.2 (excluding laboratory 5) 70 (7222) 237 (90844)
A/Anhui/IBCDC-RG5 clade 2.3 (excluding laboratory 5)
51 (0148)
195 (66262)
%GCV of titers relative to serum 0
A/Vietnam/1194/NIBRG-14 clade 1 442 (21–725) 78 (41–213)
A/Turkey/23/NIBRG-23 clade 2.2 373 (20804) 111 (29204)
A/Anhui/IBCDC-RG5 clade 2.3 306 (0812) 199 (44323)
A/Vietnam/1194/NIBRG-14 clade 1 (excluding laboratories 5, 6, 12) 39 (24–91) 82 (34–225)
A/Turkey/23/NIBRG-23 clade 2.2 (excluding laboratories 5, 6, 12) 113 (22225) 97 (25186)
A/Anhui/IBCDC-RG5 clade 2.3 100 (0198) 194 (47299)

*%GCV, geometric coefficient of variation; hHI, hemagglutination-inhibition assay using horse erythrocytes; neutralization, virus neutralization assay; min–max, minimum–maximum. Boldface indicates homologous clade 1 strain.
†%GCV absolute titer vs. relative 07/150 for NIBRG-14 (*hHI p = 0.001, neutralization p = 0.002; Wilcoxon signed-rank test).

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