Bioequivalence and Bioavailability Forum • CMDh reminder

CMDh reminder [Regulatives / Guidelines]

posted by Dr_Dan – Germany, 2012-09-28 17:32 (5022 d 09:23 ago) – Posting: # 9275
Views: 5,056

Dear Ohlbe, dear ElMaestro
Thank you very much for your valuable input

❝ I would say no. Not without a comparison to the initial analysis.

I totally agree

❝ Not only that. A major concern is the back-conversion of unstable metabolites, such as acyl-glucuronides, N-oxides etc., back to parent during sample processing. You won't see anything with ISR if you have 100 % back-conversion during processing, of course. But if you have a partial back-conversion, it is likely to vary from run to run and to be detectable with ISR (at least that's the theory). But if your unstable metabolite has turned back to parent, or has dramatically decreased, during the 3 years your samples will have spent at -20°C, you are unlikely to detect anything if you only compare a first re-analysis to a second re-analysis.

I once made the experience that one lab did not pass the acceptance criterion for ISR. The second aliquot was transferred to the biggest competitor who analysed the samples with exactly the same method and this time the analysis passed. An investigation for the reason was without any result. Maybe because the second aliquot was used? Better performance of the second lab? All other parameters were ok.
Kind regards
Dan

—
Kind regards and have a nice day
Dr_Dan

Complete thread:

Deficiency response kamblpa2 2012-08-13 10:33
- Deficiency response Ohlbe 2012-08-14 00:17
- CMDh reminder Ohlbe 2012-09-25 19:01
  - CMDh reminder ElMaestro 2012-09-25 20:21
    - CMDh reminder Ohlbe 2012-09-25 22:06
      - CMDh reminder Dr_Dan 2012-09-26 11:35
        
        Long-term storage samples? Helmut 2012-09-26 14:48
        CMDh reminder ElMaestro 2012-09-26 17:30
        
        CMDh reminder Ohlbe 2012-09-27 23:15
        
        CMDh reminderDr_Dan 2012-09-28 15:32
        
        CMDh reminder ElMaestro 2012-09-28 17:04
        
        90%+ off-topic Helmut 2012-09-28 17:48
        
        90%+ off-topic ElMaestro 2012-09-29 09:30