Most people think that the big advantage of being able to test their Coumadin levels at home would be the convenience of not having to get tested at a clinic every month. But in fact the big advantage is the more information and therefore greater control you would get from weekly testing at home.
Few people are getting those levels tested at home yet. Before my wife died four and one-half years ago we tried in vain to get medical insurance coverage for that home testing. She had had to take Coumadin for atrial fibrillation, which was probably one of the complications that she had from her diabetes.
Medicare started covering home testing for people who had mechanical heart valves in 2001. But it wasn't until 2008, a year after Catherine died, that they started covering that testing for chronic atrial fibrillation and deep vein thrombosis.
If you have Medicare the cost is minimal. Medicare covers 80 percent of the cost, and if you have a secondary supplement, it picks up the rest, $26 per month.
The cost is for renting the testing device and buying the test strips. For the weekly testing you need four test strips per month, but you get two extras to use if you have a problem with them.
Now, most private medical insurers are following in Medicare's lead in covering home testing of Coumadin levels. And a handful of companies now make it easier for us to test at home.
"Most insurers will cover home INR testing," says Tim Cady, president of Advanced Cardio Services in Carlsbad, California. "But with Medicare it's more cut and dried. Other insurers haven't yet seen hundreds of thousands of people requesting it. So it takes more time to get the approval to home test."
Almost four million people have atrial fibrillation, deep vein thrombosis, and mechanical heart valves and could qualify for home testing, he says. But only about 100,000 people are home testing right now.
A few people with diabetes have begun home testing in the three years that Medicare has made it more widely available. But many more of us who have one of the three conditions that Medicare covers are eligible for it.
"Conservatively, 15 to 20 percent of people with diabetes of Medicare age also take Coumadin, Tim says. "That's about the proportion I have seen among my customers."
Coumadin therapy is what we commonly call this condition. The generic name is warfarin, and other brand names include Jantoven and Marfarin.
Most people call the testing, whether at a lab or at home, PT/INR. PT is short for ProTime and prothrombin time, while INR is short for international normalized ratio, which measures coagulation of the blood. We use this to determine the clotting tendency of blood to check the correct warfarin dosage, any liver damage, and vitamin K status.
"The reason why people take Coumadin is to control the time that it takes for your blood to clot," Tim explains. "The higher your are on your PT/INR level the slower your blood clots. It's a fine line between too fast and not fast enough."
At a lower level you have a greater risk of stroke. But the higher your level the greater risk of internal bleeding, which can also be extremely serious.
Stroke is the bigger concern of most people. Strokes killed 139,000 people in America in 2007, the most recent year for which definitive numbers are available. This is the third biggest killer of Americans. By comparison, diabetes ranks as number 7.
Among the complications of diabetes stroke is one of the most common and most serious. The National Stroke Associations says that people with diabetes are up to four times as likely to have a stroke as someone who doesn't have the disease.
Tim knows both diabetes and stroke well. He is the president of Advanced Diabetes Supply as well as of Advanced Cardio Services. I've known and worked with him for years, ever since he worked for the company that made the GlucoWatch. Tim told me that he started Advanced Cardio Services because his father had atrial fibrillation and took Coumadin.
Medicare approved Advanced Cardio Services in April. The company provides the leading home PT/INR test machine, the Roche CoaguChek, which has about 60 percent of this market. This is in fact essentially the same machine that most labs use.
The CoaguChek claims to be the most accurate of the three home tests. "At a 95% confidence interval, results from the CoaguChek XS System are precise to within 0.44 INR, while the ITC ProTime Microcoagulation System and HemoSense INRatio System package inserts state that they are precise to within 0.76 INR and 1.20 INR, respectively."
ITC Nexus Dx offers the ProTime system and Alere San Diego now offers the INRatio2 developed by HemoSense. Also Abbott Laboratories markets the CoaguSense PT/INR Monitoring System.
Just as you have choices of coagulation meters for home testing you also have choices among companies that you can work with to obtain insurance coverage. Tim says that he knows of seven or eight firms in his business.
But Tim is almost certainly the only one who knows both diabetes and coagulation testing. He points out that knowledge is power both with diabetes and coagulation.
"You know from blood glucose testing how important it is to test more often to know where you are at," Tim said. "With this it is even more important, because if you are too high or too low you die."