TABLE 1.
Reproducibility of HAI titers is high within laboratories
| Laboratory | Intra-assay precisiona [no. of samples with results differing >2-fold from duplicate-sample results/total no. of sample pairs (%)] |
Interassay reproducibilityb [no. of assays with results differing >2-fold from repeat assay results/total no. of sample assays (%)] |
Median interassay % GCV [minimum–maximum] | ||||
|---|---|---|---|---|---|---|---|
| H1N1 | H3N2 | All viruses | H1N1 | H3N2 | All viruses | ||
| A | NR | NR | NR | 0/40 (0) | 0/40 (0) | 0/80 (0) | 41.4 [0–49.2] |
| B | 0/60 (0) | 0/60 (0) | 0/120 (0) | 0/60 (0) | 0/60 (0) | 0/120 (0) | 22.7 [0–43] |
| C | 0/60 (0) | ND | 0/60 (0) | 4/60 (6.7) | ND | 4/60 (6.7) | 40.6 [0–68.5] |
| D | 0/60 (0) | 1/60 (1.7) | 1/120 (0.8) | 2/60 (3.3) | 5/60 (8.3) | 7/120 (5.8) | 18.1 [0–91.2] |
| E | 0/60 (0) | 0/60 (0) | 0/120 (0) | 0/60 (0) | 0/60 (0) | 0/120 (0) | 0 [0–46.2] |
| Overall | 0/240 (0) | 1/180 (0.6) | 1/420 (0.2) | 6/280 (2.1) | 5/220 (2.3) | 11/500 (2.2) | 22.7 [0–91.2] |
a
NR, single replicates tested; ND, no data (laboratory C analyzed only H1N1 samples and was excluded from the H3N2 analyses).
b
A total of 10 samples/virus were analyzed in 6 assays by laboratories B to E to give a total of 60 sample assays/virus; laboratory A returned data from just 4 assays.