Pellicle and I are friends, but we have a bit of a lack of commitment as far as a meter of choice is concerned.
He made many good points about the CoaguChek XS. Its global distribution is much better than the Coag-Sense. You can buy it, and strips, in much of the world. Roche is selling an upgraded meter that takes the XS strips outside of the U.S. They have a meter that is only available if you use their testing services.
It operates by performing an electrical test on the blood, once it's deposited onto a strip and, based on the change in electrical impedance, and the code on the chip, it calculates an INR and prothrombin time. If you have certain blood issues (high hematocrit, for one), it either won't get a result, or will provide an erroneous result. Last year, they had a recall of a few batches of strips.
By contrast, the Coag-Sense meter actually detects the formation of a clot. It has a small wheel that spins during testing - deposit the blood, it mixes with the reagent, and the spinning wheel mixes blood and reagent. An optical sensor detects when the clot is formed (because the wheel stops spinning). The time is detected, and this time is divided by a value for the reagent (recorded as a barcode on the strip) to determine the INR.
The method of timing the formation of a clot is very similar to the method that labs use.
In 2013, I had a stroke because I put too much trust in a meter -- it was telling me my INR was 2.6 -- in the hospital, it was 1.7. I determined, after I got home, that I wanted to find the most accurate meter.
I tested many -- the ProTime, ProTIme 3, InRatio and InRatio 2, Coaguchek S (precursor to the XS), Coaguchek XS, and, finally the Coag-Sense. I also had tests at an anticoagulation clinic that used the Hemochron - a meter that was also used in surgeries and was reported to be as accurate as a lab test.
The InRatio was probably the worst. When my INR was high, the InRatio reported it WAY HIGH. At some times, the CoaguChek XS was also much higher than the lab (I'm talking about a full point or so higher).
The Coag-Sense was consistent. It seemed to be about .2 below the lab results. Many times, when I tested with Coag-Sense and CoaguChek XS, and also had a blood draw, the blood draw was almost an exact average of the two meters.
For me, the Coag-Sense was always around .1 - .2 below the lab results. In my mind, I'm more comfortable with a meter that may report SLIGHTLY LOWER than the labs than I am with a meter that reports SLIGHTLY HIGHER than the labs. (In other words, if both meters report 2.0, I can assume that the lab result may be between 2.0 - 2.2 or so (putting me in a fairly safe zone), but the CoaguChek XS result may mean that my INR may be as low as 1.8). FWIW, the meters are considered accurate if the INR reported is within 20% of the actual INR.
And, FWIW - I've had some really inaccurate results from labs over the past year or so. I'm trusting my meters more than I trust the labs.
Now -- a few more things:
I've seen some on this forum trying to make a big deal about 'extra steps' needed to do a test with the Coag-Sense. With the CoaguChek XS, you can touch the blood drop on the side or top of the strip. This IS easy. If you don't have the dexterity, you can use a capillary tube to collect the drop, then deposit it on the strip.
The Coag-Sense is a physical method of testing, so it's somewhat sensitive to air drops somehow mixing in with the blood sample. Their method requires a simple capillary tube to transfer the blood. Here's the terribly difficult method for testing with the Coag-Sense - incise finger, squeeze drop, place transfer tube onto blood drop. The blood will be brought into the tube, until it touches a tiny white obstruction - place the tip of the transfer tube into the well on the strip, and press the plunger on the transfer tube. This method assures that the right amount of blood is collected, and reduces the possibility that an air bubble is deposited onto the strip. It's really very simple. It doesn't feel like much of an 'extra step' and, in a way, it almost seems like fun.
Another thing -- CoaguChek XS strips are very sensitive to exposure to air. They come in a tube with a tight cap. Once you insert a strip into the meter, it expects a sample very soon - if you can't get an adequate drop of blood, the test fails, and the strip is toast.
The Coag-Sense is more robust. If you can't get a drop of blood onto the strip, you can put it into a plastic bag (and may not even have to do this), and use it later.
One final thing:
Cost.
There's a sexy new model called the PT2. It has lots of bells and whistles and seems to have been primarily designed for clinics, medical offices, and hospitals - it can store 2000 test results (at a test a week, that's around 40 years of tests), has WiFi, USB, an ethernet port, and NFC reader, USB, and an internal battery. It's a really nice meter. But, yes, it's not cheap (but neither are new CoaguChek XS meters).
I've seen the original Coag-Sense meter on eBay for less than $200. It's a very solid meter and, in some ways, better than the new model (it's better because it warms up faster, if that's important to you, and has no fancy features -- it just does the job). Both use the same strips. The meter for sale on eBay is supposedly new - it may be - I don't have one, so I can't speculate. I think Coagusense (the company that makes the Coag-Sense meter) may have discontinued this model (PT1) when it started shipping the new model (PT2) and may have sold off inventory --- but this is just a guess. I have no idea how the vendor got these 'new' meters.
I've seen strips for sale, retail, for about the same price as the CoaguChek XS strips. I've seen them on eBay for as little as $1 - $3 each.
I'm pretty confident that the manufacturer will be around for quite a while. You should be able to get strips for many years to come.
Roche should be around for MANY years. (A few years ago, they discontinued the CoaguChek S. There was plenty of warning in advance of its removal from the market -- it makes me wonder, just a bit, what will happen if Roche expects to phase out the XS?)
To me, what I perceive to be better accuracy - results equal to, or slightly lower, than an accurate lab argues for the Coag-Sense.
(I may have an extra, barely used, Coag-Sense, if you're interested).
As Pellicle noted, measuring INR isn't an exact science. Either meter should be fine for weekly testing. The strips cost about the same - and you may be able to get a deal on eBay. Either should do well for you until (or if) they find an alternate medication for valvers that doesn't require the weekly testing. (If they do, I wouldn't be surprised if it's around $8 a dose and dreadfully difficult to reverse - keeping warfarin as an attractive, affordable alternative).
I know that I went on a bit, describing some of the differences between the XS and the Coag-Sense. For me, I prefer the Coag-Sense and have little fear that the manufacturer won't be around for a long time.
I have no financial interests in Roche or Coagusense. These are just my opinions, based on my experience with the meters.
If you have any questions, feel free to send me a private message.
