Bioequivalence and Bioavailability Forum • Outlier tests: forget it!

Outlier tests: forget it! [Bioanalytics]

posted by Helmut – Vienna, Austria, 2010-01-19 20:16 (6007 d 00:43 ago) – Posting: # 4620
Views: 9,539

Dear Ohlbe!

❝ Sorry, but I disagree there. You may exclude a standard sample, but I can't see how you could exclude a QC, unless you have an excellent and documented analytical reason to do it. And when I say documented, I don't mean just writing "sample processing error" in your raw data just because the QC fails, but rather something like no internal standard added, or sample not injected, or chromatographic interference. Your QC result is an experimental result, like it or not, outlier or not.

Disagree. FDA (2001, pages 13 and 16):

Acceptance criteria: At least 67% (4 out of 6) of QC samples should be within 15% of their respective nominal value, 33% of the QC samples (not all replicates at the same concentration) may be outside 15% of nominal value. In certain situations, wider acceptance criteria may be justified.
Quality Control Samples: […] At least 67% (four out of six) of the QC samples should be within 15% of their respective nominal (theoretical) values; 33% of the QC samples (not all replicates at the same concentration) can be outside the ±15% of the nominal value. A confidence interval approach yielding comparable accuracy and precision is an appropriate alternative.

(my emphases)

That’s exactly my example: one value below –15%, but overall bias and precision within ±15%. Of course the value has to be reported and included in the calculation of acc./prec. I don’t get the rationale why you would allow for exclusion of a calibrator (if not changing the model, according to FDA), but not a QC (both spiked matrix, etc.)

BTW, even the term “outlier” with n=2–3 is crazy.

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Helmut Schütz

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Complete thread:

outliers test for QC sample mathews 2007-10-11 07:58
- outliers test - but not for QCs! Helmut 2007-10-11 15:31
  - Outlier test - but not for QC's yuvrajkatkar 2010-01-19 08:49
    - Outlier test - but not for QC's H_Rotter 2010-01-19 12:55
    - Outlier tests: forget it! Helmut 2010-01-19 17:36
      - Outlier tests: forget it! Ohlbe 2010-01-19 19:00
        
        Outlier tests: forget it!Helmut 2010-01-19 19:16
        
        Outlier tests: forget it! Ohlbe 2010-01-19 21:00
        
        QCs vs. calibrators Helmut 2010-01-19 21:49
        
        QCs vs. calibrators Ohlbe 2010-01-20 19:01
        
        QCs vs. calibrators Helmut 2010-01-20 19:26
        
        QCs vs. calibrators Ohlbe 2010-01-20 19:52
        
        Two thirds of QCs H_Rotter 2010-01-20 16:21
        
        Two thirds of QCs Ohlbe 2010-01-20 18:49
        
        Outlier tests: forget it!....what if.... moblak 2010-01-25 10:04
        
        Outlier tests: forget it!....what if.... Ohlbe 2010-01-25 23:19