From Julie Tange, Developmental Technologist at Mayo Medical Laboratories:
Hi George, our lab recently brought up calibration of the INR/ISI again. I know this was a hot topic a couple of years ago and CLSI came up with a document providing guidelines. I had heard at that time that a couple of companies were developing calibrator sets to be sold commercially. However, it seems that the subject has fallen into the background and I haven’t seen any product being sold to promote INR/ISI calibration. Yes, Beckman has their verification and calibration set, but that is only for their instruments. What should I use for a “non-paired” reagent-instrument set? Thanks! Julie
Hi, Julie nice to “hear” from you. I am sorry to tell you that Beckman-Coulter, Inc has the only FDA-cleared local INR calibration kit on the market, and that, as you said, it is only cleared for use with their instruments and reagents. This is a source of frustration for coagulation laboratories everywhere, especially as local calibration is routine in Europe.
It is true that CLSI has a guideline, H54-A: Procedures for Validation of INR and Local Calibration of PT/INR Systems; Approved Guideline, chaired by Dorothy Adcock-Funk, MD. Here is the CLSI summary description:
This document describes the use of certified plasmas to enhance performance of the prothrombin time (PT)/International Normalized Ratio (INR) system test; reviews limitations of the INR systems that may occur when a manufacturer-determined ISI is used without local verification or calibration; and provides a rationale for performing local ISI verification with recommendations as to when PT calibration may be indicated.
Two companies (that I know of) have brought kits with acceptable technical parameters to the FDA and all have failed to clear. It seems that for now, we have to continue to rely solely on manufacturers’ ISI. Geo.