Table 2. Dry swab versus other sampling methods for 28 locations, Brentwood postal facility, December 17–19, 2001.
| Method | Dry swab |
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|---|---|---|---|---|---|---|
| No. concordant samplesa |
No. discordant samplesb |
Correlation |
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| Positive (%) | Negative (%) | Dry positive | Dry negative | rsc | p valued | |
| Wet swab | 4 (14) | 15 (54) | 0 | 9 | 0.43 | 0.024 |
| HEPA vacuum | 4 (14) | 5 (18) | 0 | 19 | 0.21 | 0.282 |
| Wipe | 4 (14) | 5 (18) | 0 | 19 | 0.07 | 0.719 |
aTwo samples from the same location are concordant if both positive or both negative for Bacillus anthracis spores. bTwo samples from the same location are discordant if one is positive and the other negative for B. anthracis spores. crs denotes Spearman’s correlation coefficient between level of B. anthracis (CFU/cm2) obtained by using the dry swab method and the level of B. anthracis obtained by using the comparison sampling method. dp value for null hypothesis of zero correlation.