iSTAT PT Plus transition

Does your red top have a clot activator in it?  We usually use the white top tubes for our i-STAT correlation (blue on the Stago) and test immediately.  

Yes, I experienced the same, even when comparing the current PT/INR cartridges to the new PTplus results.  I've already finished my validations and had the data "crunched" by Abbott, although awaiting a few other details before having it reviewed by our medical director.  It seems to highlight why the INR is used - the INR's compare pretty well.  The algorithm is different since the PT is measured a little differently in the PTplus cartridge (I'm paraphrasing...).

Thank you Deb! Since you have completed, does that mean your validation passed even with the difference in PT results?

thanks Lori! No, our red top is a plain tube. We do not have the white tubes.  

Red tubes are not actually plain tubes--if it says "serum" on it, it contains a clot activator. You would need to use a tube that says "No additive" we use the clear/red tubes that are used as a waste before drawing a blue top

I haven't had my medical director review the data yet, so it still remains to be seen.  We did our study using all fingerstick samples, since that's how we do them now at this location. I called CAP and they said I can validate the PTplus against the PT/INR cartridges, so I was able to avoid venipunctures altogether.  Good luck!

Good Morning,
We are also experiencing the issue of the new ISTAT PT Plus cartridge not correlating with main lab. We use the ACL Top in the main lab. We have been collecting venous samples in a plastic syringe, dosing cartridge immediately, then filling blue tube for ACL Top testing. Are TAE is +/- 0.4. PTPlus INR results are consistently running lower than main ACL Top. I have reached out to Abbott and sent them all our data and collection information. I am waiting to hear back from them. 

PT seconds will definitely not correlate across different methods, essentially why the INR was created all those years ago.  

I was under the impression that no additive plain red tops still had clot activator in them? @Lori Pattison can you confirm if the white top you are using has any additive? 

@ Faith Benjamin.  Here is the white top info: The Vacuette Venous Blood Collection Tube Plain Sterile Clear Tube features a Z No Additive tube. This means that the tube does not contain any additives or anticoagulants. It is suitable for collecting blood samples that do not require any additional testing or analysis.

@ Lori Pattison, thank you!

Can anyone tell me the minimum samples they used for the sample imprecision piece?

How are you all justifying the difference in results? My initial thought is that we will not be able to use the PT Plus cartridge because it does not correlate to lab, but am I missing something? Based on the responses I am getting, it seams like some of you expected a difference but are still going to continue to use them. What are you going to tell the physicians when they see the difference? 

@Amanda POC devices will have differing methodologies than the lab counterparts. The goal is to evaluate the methods against the reference to understand those differences and how it can affect patient care. Ultimately the total clinical picture is what the clinician and their teams should be looking at to guide diagnosis, treatment and monitoring. All of that to say, the medical director for your facility will make the final decision regarding acceptance - data fruit salad (thinks apples to oranges) is not uncommon in the POC world but should not be a determent from their use in practice. 

Hi Amanda,
We don't report the PT.  We "old timers" remember when INR hadn't been created yet.  We reported the PT and the normal control so physicians could compare PTs done on different analyzers.  The PT's didn't match from analyzer type to analyzer type.  In very simplified terms, the INR is a calculation that takes away that variation between methods so they are comparing apples to apples.  For this iSTAT thing, it's like the PTplus cartridge is a different method than the PT/INR one.  It won't, and doesn't have to, compare for the PT.  Just the INR.  Some patients do their own testing at home on all kinds of meters and then sometimes come to the clinic to have it done or even to the hospital to have a lab drawn venous one.  The INRs should compare, but the PT may or may not.  Hope that helps some!  Deb