Table 2. Reactivity in Blood Donor Populations.
| Method | Number [Percent] Negative1 (95% C.I.)2 |
||
|---|---|---|---|
| Non-Endemic | Endemic | Total | |
| C6 ELISA | 509 [99.2%] (98.0, 99.8%) |
1311 [98.6%]3 (97.9, 99.2%) |
1820 [98.8%] (98.2, 99.3%) |
| Two-Tier (WCS ELISA/WB) a | 512 [99.8%] (98.9, 100%) |
1321 [99.4%]3 (98.8, 99.7%) |
1833 [99.5%] (99.1, 99.8%) |
| Two-Tier (C6 ELISA/WB) b | 513 [100%] (99.3, 100%) |
1320 [99.3%] (98.7, 99.7%) |
1833 [99.5%] (99.1, 99.8%) |
| WCS ELISA | 492 [95.9%] (93.8, 97.4%) |
1283 [96.5%] (95.4, 97.5%) |
1775 [96.4%] (95.4, 97.2%) |
| N (total # donors) = | 513 | 1,329 | 1,842 |
| P* | 0.38 | 0.006 | 0.002 |
| P† | 0.13 | 0.004 | <0.001 |
1
% Negative calculated as (Total # samples – Total # Reactive Samples)/Total # Samples
2
calculated by the Exact Method
3
one donor serum which was positive by both C6 ELISA and IgG immunoblot, but negative in WCS ELISA, was categorized as two-tier negative.
a
Two-tier testing with WCS ELISA as 1st step and IgG + IgM Western Blot as 2nd step
b
Two-tier testing with C6 ELISA as 1st step and IgG + IgM Western Blot as 2nd step
*
For the comparison of C6 ELISA with WCS ELISA-based two-tier testing
†
For the comparison of C6 ELISA with C6 ELISA-based two-tier testing
Abbreviations: WCS, whole cell sonicate