Gamma Validation vs. Quarterly Dose Audit Differences


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Can anyone define difference between Gamma Validation and dose audits

We have just completed/about to complete Gamma Validation including Bioburden determination, Dose verification, Sterility test and Dose Mapping (in progress) using the VD max25 method

What is the frequency for dose audits using VD max25 method:

1. Do I need to perform whole gamma validation exercise for every three months, which means Bioburden determination, dose verification and sterility test, dose mapping


I can just do bio-burden determination of 10 samples and sterility test for 10 samples every three months. Once I get enough history on bio-burden then I can perform Gamma Validation on annual basis.


I have to do bio-burden determination of 10 samples, dose verification of 10 samples and sterility test of the samples irradiated using verification dose

2. We have routine three month bio-burden monitoring program for other devices. (This product is not a family type product)
3. Average Bio-burden we determined for initial 3 batches is 50 CFU as part of this gamma validation exercise

4. VDmax25 method is choice of method as we will be manufacturing devices as per customer requirements for e.g. one batch in every 6 months

Sorry my questions sound bit confusing, as I am very much confused to get the basics clear :confused:

Ronen E

Just a person
Super Moderator
1. Are you working according to ISO 11137?

2. 50CFU is not overwhelming but it's also not too good. I would look at initiating a preventive action to see what can be done to lower it.

3. Apart from CFU count I'd also look at what sort of organisms are present. Some types call for action even at 1 digit counts. If you have spore-formers in your clean environment you will probably want to do something about it.



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I wouldn't be overly concerned about the 50cfu as long as it under control....the VDmax25 method is suitable for up to 1000cfu. In fact having an overly low CFU makes it difficult to set warning/action limits and small changes may knock your validation out

From what I recall you will need to do VDmax validation and dose mapping initally, you then need to do a dose audit on a quarterly basis or batch basis (whichever is more appropraite). The dose audit is similar to the initial VDmax but just confirms the initial assumptions are still valid. After a suitable period of time you can drop down to annual dose audits

As a matter of routine I carried out bioburden on every batch, except when a dose audit was conducted as this will include bioburden analysis.

We never carried out sterility tests except as part of initial validation/dose audits.


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Thanks pkost,

Our VDmax validation part is complete including dose mapping.

Now for next dose audit I need to perform following steps:

1. 10 samples irradiate at 8.8 kGy (Dose Verification)
2. Send these 10 samples for Sterility test
3. Verify the results

Can you recommend the above steps as part of the dose audit or correct me if I am wrong.