An important aspect that - depending on the type of method - is evaluated during method validations according to the ICH Q2(R1) guideline is precision. This includes repeatability as well as intermediate precision (inter-assay precision).
Intermediate precision examines the variability of the results, which are obtained under changing conditions common in the laboratory. This includes different laboratory technicians who are performing the method, different days on which the method is done and / or different instruments that are used for analysis (e.g. 2 different photometers). To examine these different aspects, you can either consider each aspect individually or you can apply the so-called "matrix approach" (experimental design) for intermediate precision, which kills all aspects with one stone ;-)
The matrix approach is illustrated in the following table:
|* 2 different photometers / HPLC systems / etc.|
It consists of 6 experiments, in which 2 technicians carry out the experiments over 3 days using 2 different instruments. The sample is analyzed at 100% target concentration. For evaluation of the intermediate precision matrix approach, mean, standard deviation (SD) and relative standard deviation (RSD) are calculated and finally the relative standard deviation is compared to a previously defined acceptance criterion (e.g. RSD must be ≤ x%).
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