Kim Kinney at Clarian brings question only when she has a really tough problem, as she can resolve most coagulation issues that come along. She is converting her central lab and a number of satellite labs from MDA to Beckman-Coulter Inc. (BCI, TOP) instrumentation, and most recently is moving her factor V and VII activity levels to the new instrument and reagents. Factors V and VII assays are based on the prothrombin time reagent, and although it is rare to have a single factor V or VII deficiency, they are often assayed to confirm liver disease and to distinguish the coagulation effects of liver disease from vitamin K deficiency.
Anyway, her problem is this…
She ran frozen normal aliquots on the old and new platforms and the new normal ranges nearly match the old. However, she is now running frozen patient aliquots on both, and the BCI instrument and reagent combination is reporting significantly lower results than the old MDA. She wonders what to do next.
Kim, I may not have the answer so I’ll start by soliciting support from our blog participants. Those with experience, please help.
Meanwhile, I’ll start by assuming you are running the two systems side-by-side. If you are using old normal or patient results for your aliquots, they may be affected by storage issues. Second, I assume you are only comparing patient aliquots and no purchased controls. Purchased controls, especially if lyophilized, may generate matrix effects that respond differently to reagent/instrument combinations. Third, I assume there’s been no reagent or instrument change between when you ran the normals and the patients. Given those conditions, I suggest you first repeat the normal range on your existing aliquots, then (gulp) consider preparing a new set of normals.
I have one question for Kim and another for participants. For Kim, are you also running factor II assays on a PT platform, and if so, how are they coming out?
My question to participants may be heresy. I wonder how precise we need to be with our normal ranges for factors other than VIII or IX? How many of us revert to textbook ranges?