30 replies to this topic

[Charles.C]

Hi Wayne,

No need to apologise since I am currently 'in the bush' myself for a few weeks.
I agree yr comments, particularly about the inter/intra aspects. Actually I suppose serology is still the "primary" standard. particularly for those who can't afford PCR. I guess people have become somewhat accepting of the AOAC credentials / self imposed tolerances based on experience and awareness of the practical difficulties which you noted.
Justifying the validity of the AOAC choice would generate a nice topic on its own (especially for the statisticians).

Rgds / Charles.C

[wayne]

Hi Charles C

Welcoming back. I hope you had a nice time in the "bush". What was the weather like in your part of "the bush" ?

Serology (including monoclonal antibody) has a similar weakness as what the PCR has. It picks up all specific antigen ( including death cells) - correct me if I am wrong. So, the rsults are invalid for validation of the effectiveness of, say a heat treatment. Apparently, we still have to rely upon a culturing method.

Again, enumeration errors are high ( insensitive) for most of the common culturing methods ( such as the pour plate method etc etc). It will be good if someone can validate the sensitivity of each AOAC's method and then link it to food safety validation. Would it be an interesting research topic?

You are right, we are confronting with practical difficulty in the area of validation. Can an auditor issue a non-conformance for this, as the validity of an analytical method chosen could not be confirmed?

Regards/Wayne

[Charles Chew]

Can an auditor issue a non-conformance for this, as the validity of an analytical method chosen could not be confirmed?

Dear Wayne,

Thank you for bringing forth the above issue. While I welcome back Charles C. and as always, it would be great if we can link the issues that are discussed directly with food safety.

I am add that you have raised an important audit issue where clarity would assist auditees in general.

Regards
Charles

[Charles.C]

Dear Wayne,

The weather is good if you like fried eggs.
Actually when I suggested serology, I meant the end result of a culturing procedure so perhaps we are in agreement there.

I would hope that anyone who can plough through all the posts / links in this thread will get some idea of the complexity of specifying the relationship between food safety and mic.criteria / measurements(not to forget the non-safety parameters also) . As you say, substantial errors (confidence intervals) are involved in some estimates. I guess the challenge here is to prioritise and set meaningful criteria which are workable within these restrictions. The EU's 2006 mic. standards have attempted to follow such logic so as to rationalize existing standards. Nonetheless the zero tolerance requirements here and there are obviously still debatable as per this thread.

Regarding the auditor query, I don't have a copy but does not ISO 17025 specify the minimum internal requirements for validation of laboratory procedures ??

Rgds / Charles.C

[wayne]

Dear Charles C

I would think we both have a similar line of thought regarding C=O as well as the sensitivity/reliability of the serological & culturing method when these are linked to food safety control measure validation.

Charles Chew is right; it is an important issue when comes to FSM system validation.

Indeed, I would like to obtain opinions from food safety auditors from this forum. However, they are hiding somewhere and shy away with their talent.


I repeat my question here for clarity ' Can an auditor issue a non-conformance to an auditee if the validity of his/her analytical method(s) cannot be confirmed'?

I would think there are dozens of food safety auditors registered with this forum. Where are they? Simon, can you help?


Regards/Wayne

[Franco]

' Can an auditor issue a non-conformance to an auditee if the validity of his/her analytical method(s) cannot be confirmed'?