From Siddhartha Sharma: Can you please throw some light on the concept of AMR and CRR for coagulation testing instruments? Thanks.
I went to Dr. Larry Brace, Edward Hospital in Naperville, IL for this question. He responds that a current CAP requirement is for each assay to have an established analytic measurable range (AMR) and a clinical reportable range (CRR). That is, the AMR is how high your assay can measure and still be reportable (linear) before making a dilution. The CRR is how high you want to report. The CRR can be the same as the AMR, or you can dilute; CRR defines this. In some assays, you can dilute infinitely until you get something that falls into the AMR before accounting for dilution. In other assays, matrix changes define how far you can dilute. If you can only dilute 2x before you run into matrix effects, the the CRR is 2 times the AMR. I hope this is helpful.
Thank you, Larry, this explains it for me. Of course, the AMR and CRR would need to be defined for each assay and instrument. Geo.
Hello, Siddhartha, Subsequent to my last post, I also heard
Hello, Siddhartha, Subsequent to my last post, I also heard from Lisa Reid-Fifoot at Precision BioLogic. Lisa says the decision whether to dilute and assay Vs. just reporting >the upper limit is a local decision. Like you, I suspect laboratory directors are likely to dilute and report factor assay results, but I know of no one who dilutes a PT or PTT. Most will just relay the instrument’s verbiage; for instance, greater than 300 seconds (or some such phrase).
Dear George and Larry,
Thanks for your response. I would
Dear George and Larry,
Thanks for your response. I would like to know whether the same will hold good for tests like PT and PTT measurements where the instruments measure the rate of clot formation which I doubt can follow a linear trend. The same can be applicable to the factor assays though. Please clarify on the same. Thanks, Siddhartha.