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janmacek ☆ Czech Republic, 2012-12-10 12:47 (4948 d 02:03 ago) Posting: # 9703 Views: 4,227 |
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Dear colleagues, I know that all people use the following criterion for incurred samples: the difference between original measurement and reanalysis should be lower than 20%. However, the Guideline on bioanalytical method validation has different wording: "The concentration obtained for the initial analysis and the concentration obtained by reanalysis should be within 20% of their mean for at least 67% of the repeats." What does it exactly mean? For example, if X1=81 and X2=119, their mean is 100, 20% of the mean is 20. So the concentrations are within 20% of their mean if they are within the interval 80-120. Please note that the Guideline does not speak about difference of the measurements, mathematically I understand this statement as two conditions for X1 and X2 that must be fulfilled simultaneously. I am aware of the fact that my opinion is provocative, but is it wrong? With best regards, Jan |
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Ohlbe ★★★ France, 2012-12-10 13:37 (4948 d 01:14 ago) @ janmacek Posting: # 9705 Views: 3,527 |
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Dear Jan, The wording in the guideline is indeed unclear. I know it has been pointed out a couple of times at various workshops. What I heard is that the PKWP would consider issuing a clarification if confusion was seen in future. Regards Ohlbe — Regards Ohlbe |
Ing. Helmut Schütz