- At what INR would they repeat the point of care (POC) prothrombin time and international normalized ratio (PT/INR)?
- At what INR would they do a central laboratory (plasma-based) INR to confirm the POC INR?
- Regarding the correlation between CoaguChek INR and central lab (plasma-based) INR how much does the reagent source of lab INR affect the results. Roche use a recombinant thromboplastin.
Hello, Joyce, and thank you for this important question. We had some discussion of when to compare POC PT/INRs to the central laboratory plasma-based PT/INRs in 2012, referenced in these links:
Our discussions centered on whether to use INR 4.0 or 5.0 as the trigger point. The results of our Quick Question survey seems to strongly favor 4.0. Consideration was also given to thromboplastin reactivity, with preference going to the reagents whose international sensitivity index (ISI) is near 1.0. There was some discussion about whether it was necessary to make systematic comparisons with plasma-based INRs at all, though it seems most make that their policy.
The Clinical and Laboratory Standards Institute approved guideline Point of Care Monitoring of Anticoagulation Therapy, POCT 14-A, (formerly H 49-A) does not address comparison to plasma-based PT/INR reference results. For this reason, I’m contacting one or two guideline authors and other experts for opinions and references. Check back soon, as we may have additional input. Geo.