BLOOD COAGULATION STUDIESPT—Prothrombin Time; Pro Time; Protime

aPTT/PTT—Activated Partial Thromboplastin Time

INR—International Normalized Ratio

WHAT DO THESE LAB TESTS MEASURE?

PT and INRProthrombin Time and

International Normalized

Ratio

The PT test measures how long it takes for a clot to form in the sample of blood

The reagents that are used to perform these tests vary from lab to lab. This causes normal values to fluctuate

INR with PT tests was set by the World Health Organization (WHO) to standardize the results across the world.

WHAT DO THESE LAB TESTS MEASURE?

aPTT or PTTActivated Partial

Thromboplastin Time

The PTT test measures the functionality of the intrinsic and common pathways of the coagulation cascade.

WHY ARE THESE LABS ORDERED?

PT and INRProthrombin Time and

International Normalized

Ratio

Detect how well the

patient’s blood thinning

medication is working to

prevent blood clots

To confirm a patient’s blood clotting status prior to surgery

aPTT or PTTActivated Partial Thromboplastin

Time

To monitor standard heparin anticoagulant therapy

To investigate an episode of unexplained bleeding or thrombotic episode.

WHAT IS THE NURSING RESPONSIBILITY?

PRETEST PREPARATION OVERVIEW

Perform hand hygiene Identify patient Assemble all equipment and supplies Put on clean gloves Explain procedure to patient

Explain that mild and brief discomfort may be felt

o Verify (if required) that fasting has taken place

WHAT IS THE NURSING RESPONSIBILITY?

PRETEST PREPARATION (SPECIFIC)

aPTT/PTT * If the patient is

receiving heparin by intermittent injection plan to draw the specimen 30-60 minutes before the next dose.

* With a continuous heparin infusion, specimen can be drawn at anytime

PT and INR Explain to patient

there is no need to fast before the procedure.

*If the patient receiving warfarin, the specimen must be taken before given the daily dose.

 

WHAT IS THE NURSING RESPONSIBILITY?

SUPPLIES NEEDED

Gloves Alcohol Blue-Top (Sodium Citrate) Tubes Tourniquet Needle Gauze Bandage/Tape Labels for Tube

WHAT HAPPENS INTRATEST?GENERAL OVERVIEW

Position patient to access the anticubital fossa Ask patient to make a fist to distend veins Select vein for venipuncture Apply a tourniquet above the puncture site Cleanse site with alcohol, and allow to dry Perform venipuncture at a 15-degree angle to the skin Ease the Vacutainer tube forward in the holder as soon

as the needle is in the holder When tube is filled, remove. Another tube may be

inserted into holder Release the tourniquet when the blood flow begins Properly dispose of contaminated materials List on lab slip any drug that the patient is taking that

may affect the test results.

WHAT HAPPENS INTRATEST?HTTP://WWW.YOUTUBE.COM/WATCH?V=_8ZSQXFQVQM

The nurse collects a venous blood specimen from the patient’s arm, filling the vacuum tube. The Blue-Top vacuum tube must be filled

completely to ensure a proper blood-to-anticoagulant (sodium citrate) ratio.

The sample should be immediately mixed by gently inverting the tube back and forth to ensure adequate mixing of the anticoagulant

with the blood. Properly dispose of contaminated

materials List on lab slip any drug

the patient is taking that mayaffect test results

WHAT HAPPENS POSTTEST?

Pressure or a pressure dressing is applied to venipuncture site.

The site must be monitored for bleeding. *Bleeding time will be

increased if patient is receiving anticoagulants or has coagulopathies

The nurse must also check for blood in the urine and all other excretions and assess the patient for bruises, petechiae, and bleeding gums.

Apply pressure to the venipuncture site and assess site for bleeding.

If severe bleeding occurs, the anticoagulant effect of warfarin can be reversed by the slow parenteral administration of Vitamin K.

If coagulation must be returned to normal more quickly, plasma can be given.

aPTT/PTT PT and INR

WHAT ARE THE EXPECTED VALUES? MANY HOSPITALS ARE NOW REPORTING PT TIMES IN BOTH ABSOLUTE AND

*INR NUMBERS

Normal Values aPTT: 30-40 seconds PTT: 60-70 seconds

Patients receiving Heparin, expect results 1.5-2.5 seconds greater than normal

Critical Values aPTT: < 50 seconds,

therapeutic anticoagulation may not have been met and more heparin is needed

aPTT: > 100 seconds, shows too much heparin has been given; risk for serious spontaneous bleeding exists.

Normal Values PT: 11.0-12.5 seconds *INR: 0.8-1.1

Patients receiving Coumadin, expect results 1.5-2.5 greater than normal

Critical Values: PT: > 20 seconds INR: > 5.5 * report for

patients on anti-coagulant drugs

aPTT/PTT PT and INR

INTERFERING FACTORS

Prolonging Factors Antihistamines Ascorbic acid Chlorpromazine Heparin Salicylates

Prolonging Factors Alcohol intake Diarrhea

Shortening Factors A diet high in leafy

green vegetables

aPTT/PTT PT and INR

WHAT MAY CAUSE AN INCREASE OR DECREASE IN RESULTS?

Increase Congenital clotting factor

deficiencies, cirrhosis of liver, vitamin K deficiency Disseminated intravascular

coagulation (DIC Heparin administration Coumarin administration

Decrease Early stages of DIC,

Extensive cancer.

Increase Liver disease Hereditary factor deficiency Vitamin K deficiency Bile duct obstruction Coumarin ingestion, Disseminated intravascular

coagulation (DIC) Massive blood transfusion Salicylate intoxication.

DecreaseN/A

aPTT/PTT PT and INR

REFERENCES

AASN. (18 June 2010). PT and INR. Lab tests online. Retrieved September 29, 2010, from http://www.labtestsonline.org/understandin

g/analytes/pt/test.html AASN. (18 June 2010). PTT. Lab tests online.

Retrieved September 29, 2010, from

http://www.labtestsonline.org/understanding/analytes/appt/test.html

Pagana, K. D., & Pagana, T. J. (2010). Mosby’s manual of diagnostic and laboratory

testing. St. Louis, Missouri: Elsevier Inc.