400 person study on lower INR (1.5-2.5) with mechanical valve

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carolinemc

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I home test. But the testing done before I home tested and the occasional test to check the accuracy of my Coaguchek was done via venous draw at the lab. It may be the if you go directly to the coumadin clinic for the test that the finger prick may be more common.

It will be interesting to see what the experience is of others on this.
My lab does the coag and rarely sends be to the basic lab. Has nothing to do with the post on a small-scale study. More studies have to be done to get doctors wo make that risk call.
 

carolinemc

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I think that you are wise to stay above 2.0. The study that is underway references the two previous studies which looked at lower INR range, the Proact Trial and Lowering It. Proact targeted 1.5-2.0, but there was tight INR control and the average INR for the test group was 1.89, actually very close to the 2.0 mark. This suggests to me that they were cautious to stay away from the 1.5 threshold. Lowering It, which had a target range of 1.5-2.5 for the test group had an average INR of 1.94. So, both of these trials had tight control and even though there was a low threshold of 1.5, it would appear that they probably steered clear of that. It is one thing to test weekdly and have the A Team working coagulation management. In the real world, many go 4-6 weeks between INR testing and they don't always have the A Team coagulation management in play, making it even more precarious.

These studies all play games with words as well, I have noticed. They will lump all bleeds together, not separating major bleeds from minor bleeds. Then then will say, the lower INR resulted in fewer bleeding events with no increases in strokes or heart attacks. But, when you look at the actual results you find that Lowering IT had 3x as many thrombolic events in the test group as compared to the control group. How then are they able to say that the stroke events were "similar" or the same? It is because due to relatively small numbers of participants and relatively short period of study, the number of thrombolic events was 3 for the test group and 1 for the control group. It is new math to say that there was no difference, but apparently they get a pass because the two are both relatively low numbers. Increase the number of participants by 10 fold and take the study out 20 years and they will not be able to say that there was no statisical differnce when the number is something like 100 thrombolic events vs 300.

" Two moderately-sized clinical studies showed that an INR target range of 1.5-2.5 resulted in less bleeding than the usual higher target range without increasing blood clot formation or stroke in patients with a newer valve model. "

Is this true? Not really. Lowering It found 3x as many thromboembolic events in the test group with the lower INR.

" One versus three thromboembolic events occurred in the LOW-INR and CONVENTIONAL-INR, respectively, .."


Look at how Proact uses new math to claim that a 60% increase in TE and thrombosis is "no different'

“…with no differences in the rates of TE and thrombosis events (2.96%/pt-yr in the test group versus 1.85%/pt-yr in the standard group, p = 0.178)”

The Prospective Randomized On-X Valve Anticoagulation Clinical Trial (PROACT): Lower is better, but is it good enough?

So, then in the new study, given the mathematical slight of hand, when referencing the two studies, they claim:

"..without increasing clot formation or stroke.."

Each have to make their own decision with the consultation of their medical team, but I would give some margin away from the 1.5 INR line.

Both studies found fewer bleeds in the lower INR group, but more strokes and heart attacks. Why not stick to the INR ranges that have the lowest events of all? Personally, I'd rather have a bleeding event than a stroke. That being said, some patients, who have issues with bleeding or are more prone to bleeding, might find that the trade off is worth it. I believe that these studies are valuable and give us important data. But, what I find troubling is that there appears to be bias in the presentation of the data favoring the sponsor of the studies economic interest in suggesting a lower INR is better. And, to be clear, the FDA in approving the lower INR for On-X, is not saying the lower INR is better. They just found that the number of events in that lower range to be reasonable.
The lab i use, does coag and if the pro time is at 4.0, the regular lab I go. They would never go by a small study.
 

carolinemc

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I'm curious what regions/countries still do venous draws for routine INR management? My experience has always been that clinics use finger sticks.

After my AVR, I went to a coumadin clinic for about a year before switching to home testing. They always used a finger stick and portable device. That was 16 years ago. Since then, occasionally, I had my INR tested at several different clinics. They all used a Coaguchek device.

The only times, I had INR tested via lab was when I specifically asked for it to be added as part of my annual physical where they were drawing blood anyway for lipid and other typical tests as part of the physical.
It depends on the hospital standards. I switched to a teaching school who uses coag and regular lab if the INR is above 4.0.
 

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