PT/INR Testing is Important

Ignoring Your Prescribed PT/INR Testing Can Be Very Dangerous

Any nurse who works daily in a coumadin or anti-coagulation clinic will tell you that one of the most frustrating aspects of their job is calling patients every day to see if they have followed through with their PT/INR testing. Some anti-coagulation clinics in metropolitan areas maintain, and keep track of hundreds of patients and the amount of phone calls to patients takes up a lot of time and energy.

Why all the phone calls?

Patients who are prescribed anti coagulant medications like Heparin and Warafin for conditions like Deep Vein Thrombosis (DVT) are trying to prevent blood clots from forming in their vascular systems. A clot that forms and travels through the veins to the heart, or lungs is dangerous and in some cases deadly. The prescribed drugs aid in thinning the blood making clots harder to form.

Thinning a patient’s blood to prevent clotting is good, but it has to be monitored closely to make sure that the blood is thinned to the right level. Thin is good, too thin is not good. (Imagine cutting yourself while shaving and having that little nick not close — for a long time.)

Many patients become negligent and non compliant with the regular medical testing that is required to stay on top of just how their blood is reacting to anti coagulant drug therapy. This is why nurses have to call patients, to try to get them to follow through with monitoring of the anti coagulant in their systems.

Lets face it there are many more things anyone would rather do than to go to either a hospital, clinic, or patient service center, to give a blood specimen. There are needles involved, time, and travel. This is an interruption, but it is a necessary one.

Quite often a patient undergoing anti-coagulation therapy will just brush this testing off.

The PT/INR test is performed on a blood specimen that the patient undergoing anti coagulation therapy provides.

The PT portion of the test means Prothombin Time and it is a measurement of the amount of time it takes the blood to clot in a medical testing laboratory environment.

A laboratory technician will spin the collected specimen (blood) in a centrifuge to separate the plasma from the blood. They will then add a reagent to the plasma portion of the specimen, which will cause the blood to clot. The amount of time the specimen takes to clot is then measured in seconds.

The INR half of the test or International Normalized Ratio is a yardstick of sorts. The reagents used to force the serum sample to clot are not all uniform. (There are slight variations from batch to batch) so each batch is measured individually and given a factor by the manufacturer that is then compared to a control sample that is the standard. This is sort of like a recipe that asks you to cook something at a certain temperature for X amount of time, but because the true temperature of most ovens compared to the knob you set it with is off most cooks will cook something either a little less or a little more based on what they know about their oven. The known INR (International Normalized Ratio) is used in conjunction with the known factor of each different batch of reagent and the PT (Prothombin Time) result to get a ratio.

These two numbers the PT, and the INR are important to know if you are a patient taking any anti-coagulation medication. It’s important to see if your dosage is keeping you at the right level so that a nick or a cut won’t cause a trip to the ER.

Follow your doctor’s advice about the frequency of testing and stick to it. Your physician monitors these numbers that can, and do change. Keeping you at the right level of PT and INR is always in your best interests.

Sources used:,

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