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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 2

Geometric mean titers and percentage coefficient of variations of absolute titers and titers relative to candidate antibody standard 07/150 for each serum sample for each influenza virus by hHI and neutralization*†

Serum sample Virus assay, antigen, and clade
hHI (GMT, %GCV, %GCV relative to 07/150)
 Neutralization (GMT, %GCV, %GCV relative to 07/150)
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
Prevaccination
B 7, 110, 72 7, 111, 86 6, 112, 85 12, 176, 202 12, 141, 173 10, 68, 223
N 6, 31, 46 5, 29, 18 5, 22, 0 14, 175, 228 13, 160, 215 10, 186, 250
J
 10, 111, 123
 8, 81, 155
 6, 43, 96
19, 175, 228
 18, 218, 309
 11, 102, 287
Postvaccination
Low
C 34, 84, 36 17, 29, 18 10, 126, 164 63, 183, 80 27, 201, 236 23, 122, 206
D 15, 141, 105 8, 110, 127 6, 68, 45 19, 232, 248 15, 215, 288 12, 98, 226
High
E 104, 133, 58 60, 96, 36 8, 128, 141 148, 191, 81 87, 159, 42 20, 118, 223
F 78, 97, 55 16, 141, 116 20, 104, 105 83, 144, 62 18, 152, 234 35, 147, 196
G 281, 152, 61 147, 102, 131 44, 163, 144 504, 132, 37 274, 217, 83 140, 103, 45
H 95, 118, 66 42, 144, 116 18, 106, 111 130, 166, 74 91, 157, 33 34, 127, 154
I 351, 125, 60 93, 91, 47 107, 75, 44 379, 199, 71 106, 207, 191 161, 136, 41
A 391, 138, 55 335, 114, 34 448, 119, 51 1,389, 86, 45 1,313,125, 76 2,893, 78, 63
L
 391, 147, 61
 398, 145, 42
 480, 108, 44
1,453, 104, 63
 1,520, 101, 85
 3,097, 73, 52
False positive (K)
 37, 120, 34
 24, 136, 135
 8, 81, 117
52, 185, 143
 44, 185, 53
 13, 112, 298
Sheep
O 48, 262, 285 30, 245, 338 17, 147, 319 216, 139, 53 148, 170, 33 49, 117, 156
P 1,857, 582, 535 1,171, 496, 487 1,338, 487, 545 7,317, 148, 196 732, 283, 144 3,806, 145, 59

*GMT geometric mean titer; %GCV, percentage geometric coefficient of variation; hHI, hemagglutination-inhibition assay using horse erythrocytes; neutralization, virus neutralization assay. (Paired samples were B and C, N and F, and J and H.)
†Overall serum samples, GMT by neutralization vs. hHI (p = 0.001, NIBRG-14; p = 0.008, NIBRG-23; p = 0.001, IBCDC-RG5; Wilcoxon signed-rank test).

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