Bioequivalence and Bioavailability Forum

Dear Ohlbe!

❝ […] The problem with CPD plasma is the large volume of buffer added to blood. It basically results in a 30 % dilution of plasma compared to EDTA-coated vacutainers. This can create differences in matrix effects and in recovery, depending on your sample preparation method.

Agree – but only if you compare different methods. If a method for citrate-plasma is fully validated according to current requirement I don’t see any reason why we should not be happy with it.

❝ […] a presentation by a French inspector at the EBF meeting in Barcelona in 2009. He reported two-fold differences in internal standard response between CPD and EDTA plasma, with also differences in retention times and peak width.

Do I recall it correctly that the method was validated in CPD plasma and partial (cross-?) validation (one batch acc/prec) was done with EDTA plasma of unknown origin? Or – more precisely – it wasn’t even clear whether the anticoagulant was EDTA at all? Of course it’s bullshit to ‘evaluate’ unknown samples with one anticoagulant (EDTA) based on calibrators/QCs with another (CPD). All the points you mentioned above might cut in. But this does not speak against CPD as such (I got this impression from your post’s subject line).
If a method is validated with any given anticoagulant I would be happy to defend it against an inspector. What arguments would he/she have? “CPD is uncommon; I have seen only methods for this drug with EDTA until now.”