Figure 1Specific detection of the influenza A (H1N1) pdm09 virus by pdm09-ICA. The result is negative if only one purple band appears, whereas it is positive if two purple bands appear. ICA = immunochromatographic assay.
Table 1Analytical sensitivity of pdm09-ICA
Dilution (HAU) |
Hemagglutination assay |
pdm09-ICA |
1:2 (21) |
+ |
+++ |
1:4 (22) |
+ |
++ |
1:8 (23) |
+ |
++ |
1:16 (24) |
+ |
+ |
1:32 (25) |
– |
+ |
1:64 (26) |
– |
+w |
1:128 (27) |
– |
± |
1:256 (28) |
– |
± |
1:512 (29) |
– |
– |
Table 2Specificity of pdm09-ICA for 20 different influenza viruses
Type |
Strain |
HAU |
Pdm09-ICA results |
H1N1 |
A/PR/8/34 |
27
|
– |
A/Brisbane/59/2007 |
27
|
– |
A/Solomon Islands/3/2006 |
28
|
– |
A/New Caledonia/20/99 |
27
|
– |
A/Swine/Korea/GC0503/2005 |
26
|
± |
H2N2 |
A/Singapore/1/57 |
27
|
– |
H3N2 |
A/Hong Kong/8/68 |
26
|
– |
H3N5 |
A/Swine/Korea/GC0407/2005 |
27
|
– |
H3N8 |
A/Duck/Ukraine/1/63 |
25
|
– |
H4N6 |
A/Duck/Czechoslovakia/56 |
27
|
– |
H5N3 |
A/Duck/Hong Kong/820/80 |
26
|
– |
H6N5 |
A/Shearwater/Australia/1/72 |
27
|
– |
H7N1 |
A/Duck/Hong Kong/301/78 |
24
|
– |
H8N4 |
A/Turkey/Ontario/6118/68 |
26
|
– |
H9N2 |
A/Turkey/Wisconsin/1/66 |
28
|
– |
H10N7 |
A/Chicken/Germany/N/49 |
27
|
– |
H10N9 |
A/Duck/Hong Kong/562/1979 |
28
|
– |
H11N6 |
A/Duck/England/56 |
28
|
– |
H11N8 |
A/Duck/Hong Kong/T37/97 |
27
|
– |
B |
B/Lee/40 |
25
|
– |
Table 3Performance of pdm09-ICA compared with real-time RT-PCR
Real-time PCR resultsa (nb) |
No. of specimens with pdm09-ICA
|
% Clinical sensitivity (95% CI) |
% Clinical specificity (95% CI) |
PPV (%) |
NPV (%) |
Positive |
Negative |
Confirmed positive (145) |
110 |
35 |
75.86 (68.29–82.1) |
— |
100 |
— |
Confirmed negative (43) |
0 |
43 |
— |
100 (91.8–100) |
— |
55.1 |
Table 4The positive rates of pdm09-ICA according to the crossing point values of real-time RT-PCR
Real-time PCR
|
No. of specimens with pdm09-ICA
|
Sensitivity(%) |
CP interval |
No. of positive |
Positive |
Negative |
<20 |
22 |
21 |
1 |
95.45 |
20–25 |
69 |
61 |
8 |
88.4 |
25–30 |
34 |
23 |
11 |
67.65 |
>30 |
20 |
5 |
15 |
25 |
Total |
145 |
110 |
35 |
75.86 |