Table 1. Results
of the Evaluation of Six Hand-held Assays for the Detection of Anthrax (B.
anthracis)
and Plague (Y.
pestis)
Organism |
Supplier
|
Sensitivity | Specificity# | Repeatability* | Robustness** | Stability | ||
B. anthracis |
|
Unpurified
spores
|
Washed
spores
|
No
target
|
Target |
+
|
||
1
|
106
|
108
|
1/30
|
97/99
|
20/20
|
17/20
|
+
|
|
2
|
105
|
105
|
10/30
|
86/99
|
18/20
|
17/20
|
+
|
|
3
|
105
|
106
|
25/30
|
93/99
|
17/20
|
17/20
|
+
|
|
4***
|
105
|
n.d.
|
7/17
|
21/27
|
n.d.
|
n.d.
|
n.d.
|
|
Y. pestis |
|
37°
C
|
25°
C
|
|
|
|
|
|
5
|
105
|
n.r.
|
1/15
|
99/99
|
20/20
|
20/20
|
+
|
|
6
|
104
|
n.r.
|
2/15
|
97/99
|
97/99
|
17/20
|
+
|
(#)
All HHAs tested positive to some degree with vegetative cells, which are the
progenitor of the spores,
but the results are not included in the data reported here. Also, the false-positive
results obtained with
interferents in the absence of target organisms are not included here. In these
studies, 107 spores or cells
were used.
(*) The repeatability is the ratio
of the number of sets of replicates that yielded identical results for each
ticket
relative to the total number of sets examined.
(**) The robustness of the assay
is reported as the number of times the HHA yielded expected results
relative to the number of tests performed.
(***) The evaluation of these HHAs was terminated midway in the
project because the testing required too
much total time. Each test had to be analyzed with a fluorescence reader, and
only one strip could be
analyzed at a time, which took 15 minutes. Thus, 10 tests would require at least
150 minutes total analysis
time. In addition, if the wicking of the solution along the pad did not occur
within the correct time interval,
the reader automatically aborted the test. Slow wicking was observed with a
number of the strips used in this
study, so the experiments had to be repeated. The sensitivity of these devices
was obtained from examining
a series of two replicates, instead of from the stringent test.
(+) Stable up to 86°C
n.d. = Not determined
n.r. = No reactivity observed