INR/PT What am I missing here?

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I'm a first semester nursing student. In our assessments/care plans, we have to list labs and the reason why a lab value is abnormal. My patient is on Coumadin; her INR was WNL (2.51) for pts on anticoagulant therapy, but her PT was off-the-charts high - 28.84. The lab reports that the norm is 9.2-12.7.

Is PT not calculated for patients on anticoagulants - which would make her PT "normal" for her since she's on Coumadin? Or is there something I'm totally missing here?

Thanks in advance!

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I believe the nomal PT is somewhere around 12 seconds...but on Coumadin you want the value to be 2-3 times higher. So 28.84 would be in the therapeutic range.

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Thank you! I had a feeling that was it, but I haven't found anything in the textbook to support my theory. I just knew if I put that it writing and handed it in that it'd be wrong and my prof would be all over it. Thanks!

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Specializes in Infusion, Med/Surg/Tele, Outpatient.

The INR (int'l normalized ratio?) is a calculation that basically standardizes PT values across laboratories & various testing equipment. You have a pt on coumadin, a blood thinner. PT - prothrombin time - is an actual time. The INR is the calculation. See http://www.lef.org/Vitamins-Supplements/ItemLC020321/PT-PTT-Blood-Test.html for a good explanation of PT/PTT and how it is related to the clotting cascade.

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Thank you! It confused me when I looked at the values because the INR was WNL, but the PT was incredibly high. We didn't go over this stuff in pharm at all - we just discussed the fact that you'll check the INR/PT for pts on Coumadin, but the PTT for pts on heparin. I figured the INR was calculated for anticoagulant therapy but PT wasn't, but I wanted to make sure. I'd rather make myself look like an idiot in front of you guys than with my nursing professors. :D It just didn't make sense that one value would be within therapeutic range but the other would be way too high. Thanks again!

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