INR/PT What am I missing here?

  1. 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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    About StudentNurse2011

    Joined: Apr '10; Posts: 89; Likes: 174
    Surgical Technologist


  3. by   kgh31386
    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.
  4. by   StudentNurse2011
    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!
  5. by   AggieNurse99
    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 for a good explanation of PT/PTT and how it is related to the clotting cascade.
  6. by   StudentNurse2011
    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. It just didn't make sense that one value would be within therapeutic range but the other would be way too high. Thanks again!