Questions on PT, PTT, and INR

  1. Hello,
    I am hoping you can direct me or me with the explanation of PT, PTT, and INR. I know that all have to do with clotting and we look at PTT for Heparin and INR for Coumadin but I get confused with what is the difference between the 3 of them. I tried reading it in my lab manuel but that was as clear as mud!

    I was hoping someone could point me in the right direction!!

    Thank you,
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  3. by   crb613
    I will try...PT= measures the amount of time taken for clot formation after reagent tissue thromboplastin is added to the sample.
    PTT= How well the the coagulation sequence is functioning by measuring the amount of time it takes for clot formation after partial thromboplastin is added.
    INR= just a set standard rate
    I don't know if that helped or not....its the best I can do
  4. by   ZASHAGALKA
    Pt is an indicator for Coumadin, PTT for heparin, and INR is an international standardization of the relationship between the two values.

    So, an INR of 1.0 would be a 'normal' relationship between the two values. An INR of 2.0 is normally the goal of anti-coagulant therapy.

    As that INR slides above 2.0, the risks of bleeding go up greatly. IF the doc is checking to see that someone has been off Coumadin long enough for tx (surgery?), they are checking to see that both PT and the relationship, the INR, are returning to normal values.

    Here's a way to remember the values w/ what they check:

    PTT Heparin: 10 letters
    PT Coumadin: 10 letters

    If you line them up right, the number of letters match.

  5. by   UM Review RN
    I like that memnonic, Tim!

    My way to remember it was by counting the T's.

    PT/INR stands for ProThrombin--one T.

    APTT stands for Activated Partial ThromboplasTin time--2 T's. I also noticed that APTT is for heparin, which usually has to be checked "Twice" as often.

    (Don't ask me why I could remember Activated Partial Thromboplastin Time just fine and had trouble remembering which test went with which med, though. :trout: )
  6. by   VickyRN
    Great information in this thread also
  7. by   3kidsmom
    Thank you everyone for your responses! I understand it a lot better.

    Thanks again!
  8. by   crb613
    OK so I gotta add the way I keep them straight! PTT= Heparin... connect the two T's looks like an H. So the PT has to be coumadin.