Help on: Validation Shows that Method is Not Linear Through Zero

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Question:
"I am currently validating an assay method as per ICH guidance. I have a problem with the linearity determination. The method has a single concentration of calibration standard and therefore I believe that I have to show that the line goes through the origin but when I run the linearity standards at the range in ICH, i.e. 80% to 120% of the assay concentration, the intercept of the resulting line is not close to zero. Can you suggest what I should do?" 

Answer: 
"If an analytical method involves the use of calibration standards which are prepared at a single concentration (more than one standard solution is commonly prepared) then the actual calibration line generated for the analysis is drawn between the calibration standard concentration response and zero. This method of calibration will only work if the line does go through zero and therefore an important part of method validation is to confirm that this is the case.

A typical assay method will be designed such that the typical response of the analyte is at a concentration level where the response is not subject to random errors, such as injection repeatability and integration in the case of an HPLC method, and therefore is significantly greater than zero.

When validating an assay method the range to be considered is usually ± 20% of the expected sample concentration, expressed as 80 to 120% in the ICH validation guidance Q2(R1). This means that it seems sensible to investigate linearity using standards prepared over this range. However, when running the method in routine analysis the linear range of the method is from 0 to 120%. To assess whether the calibration line goes through the origin involves an extrapolation of the line from 80% down to zero. With this approach it is quite likely that the line derived from the linearity study does not go through zero but the method actually is linear through zero. 

I recommend that an extra linearity standard is included in the linearity study at a concentration equivalent to 40%. This represents the actual linear range of the method and reduces the extent of the extrapolation required.”

 

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MTS Recommends... Getting it Write?

Getting It Write?

By R.D. McDowall, LCGC Europe, Volume 25, Issue 11, pp. 630-639, Nov 1, 2012 

Well written and easy to follow analytical procedures are critical in any lab but, as I often find during method transfer studies, the way a method is written can create confusion and errors. This article from Bob McDowall is a great read if you have the unenviable task of preparing procedures.

How Does the Update to Chapter 6 of the EU GMP Guidelines Affect You? - Part 2

In a previous blog post I summarised the proposed changes relating to method transfer in the public consultation document for Chapter 6 of the EU GMP Guidelines. Although the inclusion of the section on method transfer is the biggest revision to chapter 6, there are number of other proposed updates. In this blog post I will take a look at some of these.

Since the reason given for the changes is: ‘Inclusion of a new section on Technical transfer of testing methods and other items such as out of specification results’, and I have already dealt with method transfer, I will start with out of specification results. Under the section heading ‘Documentation’, there is a new requirement for: ‘a procedure for the investigation of Out Of Specification and anomalous results and Out Of Trend results’ (6.7)

The expectation that a QC laboratory will have a procedure detailing how they will deal with OOS results is long standing and most labs will already have this in place. The wording makes it clear that this procedure also needs to detail investigation of anomalous results and OOT results. These are typically investigated in the same way as OOS results.

Also under the Documentation heading, the recommendation that records are kept in a manner permitting trend evaluation has been updated to ‘should be recorded in a manner permitting trend evaluation’ with the additional sentence, ‘Any out of trend or out of specification data should be addressed and subject to investigation.’ (6.9)

Sampling is another area which has updates. In 6.11, referring to sample taking, there is an additional requirement that it ‘should be done and recorded in accordance with approved procedures.’ Therefore, if the sampling operation is not currently documented each time, it will need to be in future. In 6.12 there is an extra sentence: ‘the sampling plan used should be appropriately justified.’ It may be that the plan was devised sometime in the past and reasons which were so apparent then are no longer so clear. The requirement to justify the plan ensures that it is scientifically sound.

Under the Testing heading the paragraph regarding method validation (6.15) has been extended to include the following ‘A laboratory that is using a testing method and which did not perform the original validation (e.g. the use of a compendial method), should verify the appropriateness of the testing method.’ So even if a method is taken from a pharmacopeia its use in a particular laboratory needs to be shown to be suitable for the purpose for which it is being used. This assessment may conclude that no actual experimental work needs to be performed but some type of documentation should support this finding.

A new paragraph (6.20) has been inserted which reflects the importance of reference standards, making it clear that ‘Reference standards should be certified, qualified and verified as suitable for its intended use.’

The shelf life of analytical solutions, etc. is addressed in section 6.22. The requirement to mark with the date of preparation has been extended to opening date. Additionally: ‘Their in-use shelf life should be established/documented and scientifically justified.’

Finally, there are two new sections relating to the microbiological laboratory, these are:

‘6.21 Culture media should be prepared in accordance with the manufacturer’s requirements unless scientifically justified. The performance of all culture media should be verified prior to use.’

‘6.25 Microbiological media and strains should be decontaminated and disposed of in a manner to prevent the cross-contamination and retention of residues. The in-use shelf life of microbiological media should be established, documented and scientifically justified.’

In general, the emphasis of the updates is on scientific understanding and justification of the analytical methodology being used in the QC laboratory.

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Training Courses in London, April 2013: Analytical Method Validation & Transfer; Developing Stability Indicating HPLC Methods

In April, Mourne Training Services is offering 3 training courses in London. These are:

10th & 11th April 2013
Validation of Analytical Methods for Pharmaceutical Analysis

12th April 2013
Transfer of Analytical Methods for Pharmaceutical Analysis

15th & 16th April 2013
How to Develop Stability Indicating HPLC Methods

Click on the course titles above for more information about each course; including a course description, and a booking form containing costs and available discounts.

Submit the booking form or contact us by the 18th March to secure our early booking rate. The venue for the training is Jurys Inn Heathrow, convenient for travel by car or public transport.

If the dates don't suit you then take a look at our full course calendar for 2013. These courses are also available at our London location in November, and in Berlin (May, June & December) and Dublin (June).

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New Course: How to Develop Stability Indicating HPLC Methods

Pharmaceuticals need to be assessed for stability to support the assigned shelf life. Therefore, when analysing stability samples obtained from these studies analytical methods are required which are stability indicating, i.e. there is a measureable response which correlates with degradation, if present. HPLC is a popular technique for monitoring the decrease in drug and corresponding increase in degradation products due to its separating abilities. However, the HPLC method must be developed carefully to ensure that degradation products are both separated and detected appropriately. 

This year MTS is introducing a new 2-day course which will enable you to develop a suitable method. The course will describe strategies for performing forced degradation studies and selecting optimal HPLC method parameters to ensure that all relevant degradation products are separated.

The course dates and locations are as follows:

15^th & 16^th April 2013: Jurys Inn Heathrow, London, UK
17^th & 18^th June 2013: Steigenberger Hotel Berlin , Germany
11^th & 12^th November 2013: Jurys Inn Heathrow, London, UK
9^th & 10^th December 2013: GLS Campus Hotel Berlin , Germany

Contact us if you have any questions about the course, the full costs are detailed on the booking form, click here.

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How does the Update to Chapter 6 of the EU GMP Guidelines Affect Your Lab?

The European Commission has launched the public consultation of several revised GMP guidelines including Chapter 6: Quality Control (click here to view the document). The reason for change given is: "Inclusion of a new section on Technical transfer of testing methods and other items such as out of specification results." Since we specialise in method transfer at MTS (and offer a training course on the topic), we have put together a summary of the proposed updates. 

Although up to now the GMP guidelines did not explicitly refer to method transfer activities, for some time it has been an expectation that method transfer activities will both be performed and documented.  The updated guidance provides detail regarding the regulatory expectations for these activities. The new method transfer section is at the end of chapter 6 under the heading ‘Technical transfer of testing methods’.

The first part defines the expected pre-transfer activities: “Prior to transferring a test method, the transferring site should verify that the test method(s) comply with those as described in the Marketing Authorisation or the relevant technical dossier.” - It makes sense to check the method against the one submitted in the MA/technical dossier prior to transfer since you want to be sure that you are working on the right method version from the beginning.

It goes on: “The original validation of the test method(s) should be reviewed to ensure compliance with current ICH/VICH requirements.  A gap analysis should be performed and documented to identify any supplementary validation that should be performed, prior to commencing the technical transfer process.” - The original validation data should demonstrate that the method is fit for purpose, a key requirement before you start using it in another laboratory. The data will also provide information on the method capability, essential for evaluation of the success of the method transfer. My interpretation of the second sentence is that the gap analysis and identification of supplementary validation work is performed prior to the technical transfer process, which leaves open the possibility of using a co-validation approach for the actual transfer. 

The next part confirms that a written protocol is required for transfer (fairly standard in most laboratories) and provides guidance on what should be included: 

“The transfer of test methodology from one laboratory (transferring laboratory) to another laboratory (receiving laboratory) should be described in a written protocol. 

The protocol should include, but not be limited to, the following parameters: 

• identification of the relevant test method(s) undergoing transfer 
• identification of the additional training requirements 
• identification of standards and samples to be tested by both laboratories 
• identification of any special transport and storage conditions of test items 
• identification of the testing to be performed 
• the acceptance criteria which should be based upon the current validation study of the methodology and with respect to ICH/VICH requirements” 

These protocol requirements are straightforward. Points to note are: 

1. The requirement for documentation of the training requirements is formalised. 
2. Attention is drawn to transport and storage of samples, the purpose is to ensure that the same materials is analysed at both laboratories. This implies a comparative testing approach. 
3. The acceptance criteria should be based on the validation data. Whatever acceptance criteria were felt to be acceptable during validation may also be applied during transfer. My advice is to look at the actual data obtained when setting the transfer acceptance criteria, rather than just using the same values. This is particularly important when criteria are defined in a generic procedure.

The actual transfer is mentioned in terms of dealing with deviations and the requirements for the report are defined: “Deviations from the protocol should be investigated prior to closure of the technical transfer process. The technical transfer report should document the comparative outcome of the process and should identify areas requiring further test method revalidation, if applicable.”

Finally, it is recognised that some methods do not conform to the validation approach outlined in ICH, the particular example of NIR is quoted: “Where appropriate, specific requirements described in others European Guidelines, should be addressed for the transfer of particular testing methods (e.g. Near Infrared Spectroscopy)."

The other updates in Chapter 6 will be summarised in an additional blog very soon.

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