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Lot Conversion for CaCl2?

From Cynthia Hollis on 2-2-24: I had someone ask me why I didn’t do a lot conversion for changing lots of CaCl2 that I use in my APTT assays. I was unable to give them a satisfactory answer. Can you explain it for me, please?

From Geo: Hi, Cynthia, thanks for your question. I checked with my colleague Robert Gosselin, who is a validation expert. [See Bob’s ICSH article.] He says he’s never done lot-to-lots for CaCl2 but apparently, ISO requires all buffers and CaCl2 to be evaluated.

From Dave McGlasson, 2-5-24:

George, I have talked to people from Stago, Diapharma, and Werfen and found nothing about having to validate between kits. However, CAP does have something.  So I talked to Dr. John Olson. He says, “This is one of those questions that you don’t want to ask because you might not like the answer you get.” However, he is going to ask the resource committee to get a ruling on that.  Might take a couple of days. I also talked to Dr. Russell Higgins about this. Manufacturers do not mix different lot numbers with kits. I guess if you are using an LDT you would validate the method each time. I would definitely do it if you were making the CaCL2. However, who does that any more? This is one of those questions where you are looking for a problem. We did not address this issue when we wrote H57-A Protocol for the Evaluation, Validation, and Implementation of Coagulometers; Proposed Guideline. Clinical and Laboratory Standards Institute. 2007.

We’d be interested to learn how others do this as part of their lot-to-lot validations. Comments, please.

Comments (1)
Screening Assays
Feb 8, 2024 4:59pm

I’m with John Olson on this; don’t ask and plead ignorance. If your CaCl2 forms part of your APTT kit, then it would be included in the APTT lot evaluation. If not, the easiest way to validate the CaCl2 is to run APTT assays with the current vs new CaCl2 lots and show ‘equivalence’ by linear regression/Bland Altman plots. I suspect 40-60 samples over a wide range of values would suffice; alternatively, if you could show no changes to the control values (both normal & pathological) across a change of CaCl2, that may also suffice We used to manufacture our own CaCl2 and then it was compulsory to evaluate lot changes. With modern APTT reagents, the CaCl2 may be part of the kit, and thus can be included with the APTT reagent evaluation.

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