Bioanalytical Method Validation Fda Perspective


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This presentation focuses on guidance documents, 483s, dockets aiming to construct a robust bioanlaytical validation program

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Bioanalytical Method Validation Fda Perspective

  1. 1. Bioanalytical Method Validation: FDA perspective by Debanjan Das This presentation focuses on guidance documents, 483s, dockets aiming to construct a robust bioanlaytical validation program {DISCLAIMER: Certain details used here, pertaining to proprietorship of the project had been altered. This exercise is solely for enhancement of knowledge-base and not for any “for-profit” venture}
  2. 2. Interesting Observations:  Guidance for Industry:Bioanalytical Methods Validation for Human Studies,Dec’98  Guidance for Industry:Bioanalytical Method Validation,May’01  Warning Letters & Dockets  Views of private agencies of US & Europe, and on ICH guidelines on current trends of Bioanalytical validation.
  3. 3. Do guidance documents actually misguide you?  There had been a plethora of instances where the guidance documents had been vague and such were those conceptions which called in for 483s  Was that deliberate and vaguely conceptualized?  Or was that for you to read between the lines?
  4. 4. Reading between the lines; the safest way to keep a 483 away  Guidance documents should ideally instruct what needs to be done, not how.  However, when FDA issues one,it’s best taken care of if followed to the maximum.  Inspections, almost always, look for compliance based on the outlines given in guidance documents.
  5. 5. Thinking the FDA way: dissecting the guidance documents.  The following exercise (read anatomy lessons!) had been primarily on finding out the glitches in the FDA guidance sheets.  The idea is if we know where the trap is, we know a way to go round it!  The following sections will take each part (and subpart) of such documents (both the Dec’98 and May’01) and analyze the ambiguities blow by blow.
  6. 6. Introduction Section  Non-clinical studies are left out,although basic pharmacology and underlying principles are the same.  Use of ICH definitions are seriously restricted  Immunochemical assays are too vaguely defined,& are classically driven(based on GC & HPLC),rather than biologically.  Statements related to analytes of tissue samples and matrix requirements are unclear.
  7. 7. Background Section  “The acceptability of analytical data corresponds directly to the criteria used to validate the method”.The object of any validation exercise should be to assess the performance of the assay,not the other way round.  Linearity term is poorly dealt with.There is virtually no room for methods which doesn't conform a linearity in concentration vs. response curve.  Phrases like “predictive mathematical function” are missing which will cover any type of curve fit integral for assay development activities.
  8. 8. Reference Standard  It is unclear as to what frequency the reference materials have to checked prior to use.  The use of the term “interfering peak” is not relevant for immunoassays.  Due to limited bulk supplies it is difficult to maintain a master standard for comparison with future lots.  Any guidance on on the degree of characterization required for internal standards are missing.
  9. 9. Pre-Study Validation,In-study Validation and Method Development section(which includes chemical,microbial & ligand binding assays)  Since validation is a continued and an ongoing process, and that all validation must be complete prior to the onset of sample analysis, the guidelines of pre-study validation is ambiguous.  For In-study validation, reporting a bioanalytical data to regulatory agencies assumes that a method has undergone validation & that a written procedure for the conduct of analysis & reporting data exists. How correct is this?
  10. 10.  Method development, on the contrary, is research oriented,& might not be included as a component of validation at all!  Limit of Quantification(LOQ):”The results should be compared to those obtained from an extracted sample of analyses in matrix, at a concentration near LOQ”. The response from an aqueous solution of analyze may be different from that of analyte in matrix, due to possibility of ion suppression or matrix effect.  Unclear extraction procedures for compounds which interfere chromatographically, and which can be eluted by other procedures.
  11. 11.  Regression equation is ambiguous,and there’s a need for each method for each process used. The all-encompassing power model, a more objective tool to determine the best fit, is missing.  The criteria for LOQ & ULQ is difficult in immunochemistry methods. The calculations for 6 non-zero standards including LOQ & the calibration std at the highest conc. (ULQ) does not seem feasible.
  12. 12.  Precision,Accuracy,Recovery:Use of confusing terminologies are used.There is a difference between intraday & intrabatch.A lab may analyze several batches in one day by using several instruments(usual practice for large scale studies)  “Although recoveries close to 100 are desirable,a lower recovery of an analyte and or IS is acceptable”.The focus of assay development is the establishment of an accurate,precise and sensitive method with good selectivity & not necessarily high recovery!
  13. 13.  Quality control samples:Differences in response to QCs due to matrix effect is evident when each set of QCS are prepared from a separate source of matrix lot.  LOQ QC sample:This is run during a validation to establish the precision & accuracy at the LOQ & not to evaluate the error.Is there any degree of variation allowed?Is the tolerance of LOQ QC concentration be 20/0 ?
  14. 14. Documentation section  “all SOP, raw data, calculations of concentration & necessary sample sets are to be documented”. Inclusion of all these documentation puts an additional burden on any analytical lab. Inclusion of SOPs will add hundreds of pages of documents in each study report, even if submitted electronically,& a redundancy of effort of each submission are inevitable.  Which raw data is required? Does it refer to instrument response values?  Which SOPs are required? Do they refer to assay validation reports?
  15. 15. Doubts,Doubts,Doubts! Lets bring in Z540,ISO/IEC 17025 & Mil-Std 45662A!  What's this Z540? Why its important?  American National Standards Institute and the National Conference of Standards published the ANSI/NCSL Z540 Std dealing with calibration of laboratories, measuring equipment(part 1) & guidance on control of measuring and test equipment(part 2), which is the American National Std equivalent of the ISO guide for the determination of measurement uncertainty.
  16. 16. ISO/IEC 17025 impact.  Although its not mandatory to get an accreditation unless it’s a regulatory or a customer requirement, major customers, governmental bodies(even FDA), look into the use of accredited laboratories to perform calibration & testing. This is specially important to comply with in the European Union.
  17. 17. Mil-Std 45662A  Standard for calibration systems utilized by the military, aerospace & later by other industries. It’s a guidance having useful information regarding what is necessary in terms of establishing & documenting a calibration system which forms an essential part of bioanalytical validation protocol.
  18. 18. Conclusions  A harmonized validation program, encompassing all the finer prints of the FDA guidance documents, along with accreditation from other agencies, seems a plausible rationale to run a bioanalytical validation program smoothly without the risk of 483s.  It’s the matter of ends justifying the means, and never the other way round!