The INR, Again

Is the INR reliable?

With the assistance of Bernadette F. (Bunny) Rodak, I monitor the American Society for Clinical Laboratory Science (www.ascls.org) Consumer Information Forum for coag questions. The Forum is a place where the lay public ask questions about laboratory test results. Most of the questions that come up have to do with warfarin (Coumadin) therapy, Here is one that Bunny and I reviewed Saturday, July 14:.

A man from Egypt was traveling in the USA. He visited a “Doc-in-the-Box” in South Carolina for a routine prothrombin time (protime, PT) with international normalized ratio (INR). His result was 17s/INR 1.4. He contacted his cardiologist in Alexandria, who told him, “The INR varies from lab to lab. I will not adjust your warfarin dosage based on this INR.”

First, what you you advise the questioner?

Second, beyond entering the manufacturer’s ISI, how do you validate your INRs cross-platform to ensure they compare closely with results from other laboratories?

Thanks for your participation. Geo.