The relevant performance characteristics for method verification of a quantitative
microbiological method are:
-Intralaboratory reproducibility (intermediate precision);
-Measurement uncertainty
(U);
- Repeatability (s
r
);
-Trueness (bias).
These performance characteristics vary according to the sample matrix and in user
laboratories. Therefore each user laboratory shall determine these performance
characteristics in relevant matrices that are routinely tested. The performance characteristics
determined shall meet the specifications established in the validation study.
8.2 Number of samples and replicates tested
For intralaboratory reproducibility and measurement uncertainty (and repeatability), the study
design is based on ISO/TS 19036. This has been modified to include matrix effects when
samples are spiked.
For the study, 10 samples are required.
Only 1 representative strain of the target micro-organism is required to spike samples.
Samples can be inoculated using commercial products that are fit for this purpose (e.g.
lyophilized pellets EZ-CFU, Lenticules, Bioballs etc). Inoculation is carried out as described
in Figure 1.
If possible, the levels of contamination of samples shall cover the range of the method. At
least 3 levels of contamination should ?or shall be used.
Test the samples according to the method to be verified and the reference method (where
necessary).
Testing shall be carried out on 10 different?occasions or days and shall be performed by at
least 2 technicians working independently and with separate samples and reagents.
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