Bioequivalence and Bioavailability Forum

Dear Shweta!

❝ Dear sir,

Still a male chauvinist?

❝ I have seen different criterias for repeat analysis followed for predose sample.

Which ones? Can you give examples?

❝ Is there any Guideline that can give guidence regarding repeat analysis and accepting the repeat analysis value.

IMHO there's no difference between pre- and postdose samples from an analytical point of view. On the other hand in a cross-over study the statistical model does not allow for carry-over; in other words, predose concentrations in period 1 are a hint for analytical problems (selectivity), whereas in period 2 also for design issues (too short washout). The former is bad, the latter even worse.

Canada's TGD BE guidelines state:

In most studies, some blood/plasma/serum or urine samples will require re-assay. Criteria for identifying these samples should be pre-established.
Certain aberrant values can be identified before breaking the analytical code. These values may be attributed to such factors as:

• processing errors,
  
• equipment failure,
  
• obviously poor chromatography, or
  
• quality control samples outside pre-defined tolerances.

Other apparently aberrant values may become evident after the analytical code is broken. In some cases, the original assay value would show poor pharmacokinetic fit (but this should be applied with caution). In other cases, there may be a need to confirm a double peak. For aberrant values that have become evident after the analytical code is broken, the submission must note the reason for the repeat assay.
When the results of a repeat assay differ from the original by more than 15%, a third analysis should be performed. When three replicate analyses indicate that one is spurious, the average of the other two should be used. The criteria that were used for selection of replicates to be included in the calculations should be stated.

FDA's bioanalytical guideline states:

Repeat Analysis: It is important to establish an SOP or guideline for repeat analysis and acceptance criteria. This SOP or guideline should explain the reasons for repeating sample analysis. Reasons for repeat analyses could include repeat analysis of clinical or preclinical samples for regulatory purposes, inconsistent replicate analysis, samples outside of the assay range, sample processing errors, equipment failure, poor chromatography, and inconsistent pharmacokinetic data. Reassays should be done in triplicate if sample volume allows. The rationale for the repeat analysis and the reporting of the repeat analysis should be clearly documented.

EMEA's BE-draft states:

The Applicant should discuss the number of samples (and percentage of total number of samples) that have been re-analyzed, the initial value, the reason for reanalysis, the values obtained in the reanalyses, the finally accepted value and a justification for the acceptance.

Have an SOP in place (even better to state the procedure also in the protocol) and act accordingly. Personally I would never re-analyse a single value, but prefer to include adjacent values as well (example) in order to get some kind of internal validation (we know that acc./prec. ±15% or ±20% at LLOQ). Often seen 'not reportable result because difference >30%' is scientific nonsense, especially at the LLOQ. FDA allows to keep a subject for BE-assessment if the predose concentration is ≤5% of C_max. The same procedure is suggested in EMEA's draft.