Can someone explain PTT, aPTT, and INR?

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Specializes in Cardiac Tele, MICU RN.

I have to give a presentation in my pre conference in clinical to my instructor and classmates about this and all I have is basic info. Is there someone who can give me more info. about this and more depth so I can get a better understanding on this? thanks

Best Answer...

PT/PTT are laboratory tests that measure the clotting time (how long it takes blood to clot.)

PT/PTT are blood tests and INR is a ratio calculated from the PT.

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Specializes in med/surg, telemetry, IV therapy, mgmt.

everything you wanted to know about these three tests can be found at these two sites:

ptt/aptt:

http://www.labtestsonline.org/understanding/analytes/aptt/glance.html - to get more information on this, click on the tabs for test sample, the test, and common questions. there are also links that may be of interest to you.

inr:

http://www.labtestsonline.org/understanding/analytes/pt/glance.html - again, click on test sample, the test and common questions for more information

then, bookmark this site for information you ever need on lab tests:

http://www.labtestsonline.org/ - book mark this site - this site has been designed as a single resource where people can find up-to-date lab testing information vital to the understanding and management of their health, or the health of someone close to them. it includes test descriptions, conditions, screening guide and current news. when looking up disease conditions, the lab tests typically ordered for them are listed with links to explanations about them. make sure to check out their site map for more information about lab services.

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Specializes in Gerontological, cardiac, med-surg, peds.

These are wonderful sites, Daytonite! Thank you so much for sharing.

PT/PTT are laboratory tests that measure the clotting time (how long it takes blood to clot.)

PT/PTT are blood tests and INR is a ratio calculated from the PT.

At least a dozen blood proteins, or blood clotting factors, are needed to clot blood and stop bleeding (coagulation).

Prothrombin, or factor II, is one of several clotting factors produced by the liver. Prothrombin time (PT) measures the presence and activity of five different blood clotting factors (factors I, II, V, VII, and X). This test measures the integrity of the extrinsic and common pathways of coagulation. The prothrombin time (PT) measures the clotting time from the activation of factor VII through the formation of the fibrin clot. Adequate amounts of vitamin K are needed to produce prothrombin. Warfarin (Coumadin) is sometimes prescribed as a "blood thinner" because it is an effective vitamin K antagonist (blocks the formation of vitamin K).

The activated partial thromboplastin time (PTT) measures the function of several other clotting factors, found in the intrinsic and common blood clotting pathways. It measures the clotting time from the activation of factor XII through the formation of the fibrin clot. PTT prolongations are caused by factor deficiencies (factors VIII, IX, XI, and/or XII), or inhibitors (most commonly, heparin). Heparin prevents clotting by blocking certain factors in the intrinsic pathway.

PTT and activated partial thromboplastin time (aPTT) are basically the same thing. The aPTT has largely replaced the older PTT, which was unable to incorporate variables in surface/contact time: http://www.rnceus.com/coag/coagptt.html

PT is used to monitor treatment with warfarin (Coumadin). Once warfarin is discontinued, it usually takes several days to clear it from the system. The PTT test allows the provider to check that there is enough heparin in the blood to prevent clotting, but not so much as to cause bleeding. Once heparin is discontinued, its blood-thinning effects usually only last a few hours.

The greater the PT/PTT values, the longer it takes the blood to clot. HIGH PT/PTT = risk for BLEEDING. LOW PT/PTT = risk for blood clots/ stroke.

The INR stands for International Normalized Ratio. The INR is calculated from the PT and is intended to allow valid comparisons of results regardless of the type of PT reagent used among different laboratories (INR = [patient PT / mean normal PT]). The INR is a method of standardizing the PT for coumadin anticoagulation. Before the INR, different labs using different reagents had different controls and widely differing PT value ranges.

An INR of 1 means the blood clots "normally" for that pt. The greater the INR, the longer it takes the blood to clot.

The warfarin (Coumadin) dosage for people being treated to prevent the formation of blood clots is usually adjusted so that the prothrombin time is about 1.5 to 2.5 times the normal value (or INR values 2 to 3). A patient may take warfarin to anticoagulate for atrial fibrillation (target INR around 2.5) or for a mechanical heart valve (target INR 3). An INR of 3 means the blood takes about three times as long to clot compared with the normal value for that pt.

Which value, PT or PTT, does heparin influence?

Which one does coumadin?

Stumped?

You can find the right answer by counting to 10:

- - - - - - - - - - = 10

H E P A R I N (7 letters) + 3 (PTT) = 10

C O U M A D I N (8 letters) + 2 (PT) = 10

Here's another one:

What is the antidote for heparin overdose?

Protamine sulfate (just remember P M S)

What is the antidote for too much Coumadin?

Vitamin K (just remember the hard "C" at the beginning of coumadin!)

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Specializes in NICU.

Vicky,

WOW! You are a great educator, thanks so much for your info! This is great!

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Specializes in ICU-CVICU.

Which value, PT or PTT, does heparin influence?

Which one does coumadin?

Stumped?

You can find the right answer by counting to 10:

- - - - - - - - - - = 10

H E P A R I N (7 letters) + 3 (PTT) = 10

C O U M A D I N (8 letters) + 2 (PT) = 10

Wow! Vicky,

I read this sometime this morning...About 2 hours ago I got my HESI study materials in the mail. I popped in the practice test cd and what do you know...one of the first questions was something like "PT would be monitored in patients taking which of the following?" of course Heparin and Coumadin were choices...well, your "COUMADIN + 2" was the answer!

Thanks so much for taking the time to answer so completely!

May

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Specializes in Gerontological, cardiac, med-surg, peds.

Glad to be of assistance :)

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Specializes in Cardiac Tele, MICU RN.
VickyRN said:
Glad to be of assistance ?

Thank you so much for this, I am sure now that I have all of my information and I can't wait to share this with my classmates and my clinical instructor. You went into details, mapped it out and, great efforts to give me a lot of depth about each thing. Thanks again VickyRN and Daytonite

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Thank you for the teaching and the links!!!!!! Awesome.

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thanx for your links

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Thanks so much! I've booked marked them and going back to study some more...

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Specializes in NICU.

Thank you so much for the awesome explanation.

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Hey!!!

Great learning/teaching!!!! My favorite activity here.

My personal hint: PTT (imagine you make the two T's lower case with one cross bar to make them from LL or 11 to TT--two verticals with one cross-bar, makes an H--for heparin.)

As above: PTT and PT are TIMES--how many seconds pass for a particular part of the clotting sequence to occur. INR is a RATIO--a calculation between person taking coumadin's clotting time and a person with NO anti-coagulation going on would be. Coumadin/nonCoumadin.

Good work, teachers.

And as always, great websites Daytonite.

Papaw John

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