NeurologyAPTT, PTT, PT, INR

The Tests We All Must Pass• Chronological Order of the

Presentation– Introduction– APTT & PTT– PT & INR– Nursing Interventions– Differences– Current Research– Summary– Questions

The Cold Hard Facts

• We all die, but first we must live• We control our bodies via a large

neurological system• Depriving this neurological

system of blood flow = death• Thromboli can impede blood flow• Therefore thromboli = death

The Selfish Gene

• We all want to live• Keeping blood flowing to

neurological system prolongs life• Thromboli impedes blood flow• Antithrombolitic therapy prevents

thromboli formation• Therefore antithrombolitic

therapy prolongs life

Too Much of a Good Thing...• Too much antithrombolitic therapy =

prolonged bleeding• Prolonged bleeding decreases blood

flow to neurological system• Decreased blood flow to neurological

system can cause death• Therefore too much antithrombolitic

therapy can cause death

How to Walk the Line

• Develop tests to measure clotting factor• APTT & PTT• PT & INR

APTT & PTT

• APTT – Activated Partial Thromboplastin Time• PTT - Partial Thromboplastin Time

• Use intrinsic factors to initiate coagulation pathways• Coagulation is timed and compared to a standard• Test used to diagnosis and monitor

• 70 seconds…

PT & INR

• PT – Prothrombolin time• INR – International Normalization Ratio

• Firm fibrin clot formation initiated by tissue thromboplastin (factor III) and calcium

• Timed test

PT & INR

• Uses the equation: INR = (PTclient)x ISI PTavg

* ISI - International Sensitivity Index *

• INR = 1• INR = 2-3• INR = 2.5-3.5

Nursing Interventions

• Both are blood tests = similar interventions

• Require interventions at all stages of the test:– Pre-test– Intra-test– Post-test

Pre-Test

• Education• Client Health History– Bleeding disorders– Surgeries, lab tests, diagnostic tests

• Current and recent medications– Anticoagulants, acetylsalicylic acid,

herbs, nutritional suppliments, and nutraceuticals

Intra-Test• Follow directions• Breath normally• Avoid unnecessary movement• Identify client• Label vials accordingly• Fill tube completely• Have sample analyzed within 4 hours

Post-Test• Observe venipuncture site• Provide instructions regarding

excessive bleeding and bruising• Educate regarding prolonged APTT or

high INR• Reinforce health care provider

information or instructions• Notify client’s health care provider if

INR < 2 or APTT < 53 seconds

Where are the Differences

• INR internationally recognized and understood• APTT uses kaolin, celite or elegia acid to speed

up reaction time, therefore increasing the speed of the test

• APTT not recommended for prophylactic low-dose heparin therapy

• INR affected by more drugs• INR may be performed on samples older than 4

hours*

* A topic of current research

Current Research

• Certified Diagnostic Plasmas for INR

• Are 2.0-3.0 INR values optimal?• Obtaining INR and APTT values

using different analyzers• INR self testing by clients

Summary

• APTT value < 70 seconds • INR value 2.0-3.0• APTT and INR instrumental in

anticoagulation therapies, should be monitored closely to ensure adequate dosing

References• Cha, C.H., Park, C.J., Kim, D.H., Kim, M.J., Cho, Y.U., Jang, S. & Chi, H.S. (2010)

Direct international normalized ratio determination using multicalibrators is more responsive than the conventional method for measuring prothrombin time. International Journal of Laboratory Hematology, 32(4), pp. 392–397. doi: 10.1111/j.1751-553X.2009.01195.x

• Christensen, T.D., Jensen, C., Larsen T.B., Maegaard, M., Christiansen, K. & Sørensen, B. (2010) International normalized ratio (INR), coagulation factor activities and calibrated automated thrombin generation -- Influence of 24 h storage at ambient temperature. International Journal of Laboratory Hematology, 32(2), pp. 206-214. doi: 10.1111/j.1751-553X.2009.01170.x

• Peng, L., Yan, C., Wu, X. & Nie, L. (2009) Comparability of the results of PT–INR with local MNPT and APTTR with MNAPTT on different coagulation analyzers in China. International Journal of Laboratory Hematology, 31(3), pp. 352-358. doi: 10.1111/j.1751-553X.2008.01071.x

• Plesch, W. & van den Besselaar, A. M. H. P. (2009) Validation of the international normalized ratio (INR) in a new point-of-care system designed for home monitoring of oral anticoagulation therapy. International Journal of Laboratory Hematology, 31(1), pp. 20-25. doi: 10.1111/j.1751-553X.2007.00998.x

References• You, J. H. S., Chan, F. W. H., Wong, R. S. M. & Cheng, G. (2005) Is INR between

2.0 and 3.0 the optimal level for Chinese patients on warfarin therapy for moderate-intensity anticoagulation? British Journal of Clinical Pharmacology, 59(5), pp.582-587. doi: 10.1111/j.1365-2125.2005.02361.x

Questions?

• A wise person once observed:“Nurses are like the blood of the

health care system...without them it would die.”