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Vivalytic C. difficile
– Instructions for Use
Analytical Performance Evaluation
Analytical Sensitivity (Limit of Detection)
The limit of detection of the Vivalytic C. difficile test was determined as the
lowest concentration of analyte that can be consistently detected (≥95% of
samples tested under routine laboratory conditions using a defined type of
sample).
Inclusivity
To evaluate inclusivity, an in silico analysis (BLAST alignment) of the
genomic sequence of various relevant C. difficile strains against the
sequence of the PCR primers and hydrolysis probe used in the Vivalytic C.
difficile test for amplification and detection of the respective pathogens was
performed. . Inclusivity could be shown for strains listed in Table 2.
Exclusivity / Analytical Specificity
To exclude cross-reactivity (exclusivity), an in silico analysis (BLAST
alignment) of the target region of C. difficile against the genomic sequence
of various other pathogens representing common gastrointestinal pathogens
or closely related species was conducted. There was no evidence of an
interference (Table 3).
Reproducibilty
The reproducibility of the Vivalytic C. difficile test was established using a
panel with 3 different concentrations of C. difficile. At 3 test sites, each mix
was tested on the same set of Vivalytic instruments by the same operator
with 3 LOTs in 4 replicates on 3 days, respectively, yielding in a total of
324 observations per target pathogen. The obtained positivity rates for the
different combinations were correlated to the expected positivity rate
(Table 4a).
Repeatability
The repeatability of the Vivalytic C. difficile test was established using a
panel with 1 concentration (3x c95) of C. difficile. At 1 test site, the mix
was tested on the same set of Vivalytic instruments by the same operator
with 3 LOTs in 20 replicates on 1 day, respectively, yielding in a total of
60 observations per target pathogen. The obtained positivity rates for the
different combinations were correlated to the expected positivity rate
(Table 4b).
Interferences
Interferences were evaluated for endogenous and exogenous substances,
that are potentially present in the patient sample. Refer to Table 5 for
substances that have the potential to interfere with the test.
Clinical Performance Evaluation
Sensitivity and specificity results derived from native liquid and soft human
stool samples. Samples were collected in a clinical setting and compared
with results of reference methods.
Samples for testing with Vivalytic C. difficile cartridges were freshly used or
frozen for storage and prepared as describe above in eNAT® (COPAN Italia
S.p.A.).
In case of reference testing samples were prepared according to
recommendations of used reference methods. In total, 124 samples were
analysed. Sensitivity or Positive Percent Agreement (PPA) was calculated
as 100 % x TP/ (TP+FN). Specificity or Negative Percent Agreement was
calculated as 100 % x TN / (TN+FP). The results of the clinical performance
evaluation are shown in Table 6.
Technical Support
In case of questions please contact your local distributor or send a message
to the customer service of Vivalytic
(email: support-BHCS@bosch-vivalytic.com).
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