It’s important to monitor the amount of anticoagulation you are getting—usually referred to as your “INR”—to prevent problems. If you take too much warfarin you could suffer internal bleeding. If you take too little warfarin you may not receive any protection. Warfarin interacts with other medicines including antibiotics and aspirin. The best dose for you is also influenced by your diet because a vitamin found in some foods (vitamin K) counteracts warfarin.
Most people taking warfarin have their INR tested at an outpatient lab. If your INR is in the desired range (usually 2.0-3.0 or 2.5-3.5 depending on factors including age and risk) and is stable, you can have the test performed once each month. If you are temporarily taking medicines that interact with warfarin, are ill for several days, change your diet, or have an unstable INR you may need to have the test more often.
Having your blood drawn at an outpatient lab is far from a perfect solution. It’s hard on the veins in your arm. You could be exposed to people with contagious diseases in the waiting area. Driving to the lab, registering for the test, and waiting in line consume a great deal of your time. You might delay going to the lab until it’s convenient. As a result, you don’t get tested as often and promptly as you should.
The ProTime® Microcoagulation System by ITC lets you check your INR at home. (I will post about competing solutions in the future.) A device called the Tenderlett® is used to make a tiny (and usually painless) incision in the tip of your finger for collecting a drop of blood. You transfer the blood to a cuvette (a transparent plastic component about the size and shape of a microscope slide) that divides the blood into three channels: two control channels and one test channel. The control channels contain chemicals that force the blood to predetermined INR levels as a way of checking that the cuvette is OK and the system is operating properly.
I use the ITC tester and am very satisfied. My aortic valve was replaced with a mechanical valve in 1984. I had two serious bleeding problems during the time that I used outpatient labs for testing. I’ve had no major problems since I started testing my INR at home about seven years ago.
When I purchased the ProTime Microcoagulation System my doctor asked me to use both the home tester and the lab for the next three tests to compare the results. I was trained over the telephone to use the system and then had to demonstrate to a specialist that I understood and could perform the procedure. My measurements differed somewhat from the lab’s measurements but were within the manufacturer’s claimed accuracy. Most labs offer greater precision than I need. Staying within the prescribed therapeutic range is what’s important and the home tester seems up to the task.
The instrument is somewhat expensive but it saves money over time. Like many other health care fees, there is a big discount for paying cash. At the time I purchased my unit, the official price was approximately $2,400 but just $1,200 if you paid cash. I purchased my unit from Quality Assured Services (now Alere Home Monitoring as the result of a merger).
I discovered I could save money on the supplies by buying them from a company called MedTek in Utah. So now I can do a test that costs more than $75 at the lab in my doctor’s building for under $10 at home.
Don’t get me wrong. Many outpatient labs do a great job. But if you require regular INR tests, don’t mind doing them yourself, and want the convenience and cost savings, home INR testing could be a better way to go.
