I called them. So far no changes. So time will tell.
Coag-Sense versus CoaguChek xs and labs
- Thread starter Protimenow
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Roche was right -- tests with results within 20% of each other are considered to be within range of each other.
It sort of flies against logic, but because INR testing is not exact, we'll have to accept these relatively large variances.
My Coag-Sense values don't increase as quickly as the values in the XS. Repeat testing at almost the same time, using Coag-Sense strips from different lots, or Coag-Sense strips on two different Coag-Sense meters get results that match almost exactly.
At INRs above about 2.1 or so, the difference from the Coaguchek XS gets larger and larger - well beyond the accepted 20%.
I'm in a bit of a quandary now - I saw my 'coumadin clinic,' possibly for the first and last time yesterday. Before going to the clinic, the XS gave me an INR of 3.4. The clinic's XS gave me a 3.2 - both were well within range of each other.
But, earlier, the Coag-Sense reported a 2.3.
Both types of machines seem very reliable - a new batch of strips, or more than one of the same meter, reveal strikingly similar results. But the Coag-Sense and CoaguChek XS have a troubling gap in results.
I'm hoping that, perhaps with Coagusense, or, worst case, with the FDA, I can get an answer to the question: why are the Coag-Sense results so much lower than the lab or the Coaguchek XS?
It sort of flies against logic, but because INR testing is not exact, we'll have to accept these relatively large variances.
My Coag-Sense values don't increase as quickly as the values in the XS. Repeat testing at almost the same time, using Coag-Sense strips from different lots, or Coag-Sense strips on two different Coag-Sense meters get results that match almost exactly.
At INRs above about 2.1 or so, the difference from the Coaguchek XS gets larger and larger - well beyond the accepted 20%.
I'm in a bit of a quandary now - I saw my 'coumadin clinic,' possibly for the first and last time yesterday. Before going to the clinic, the XS gave me an INR of 3.4. The clinic's XS gave me a 3.2 - both were well within range of each other.
But, earlier, the Coag-Sense reported a 2.3.
Both types of machines seem very reliable - a new batch of strips, or more than one of the same meter, reveal strikingly similar results. But the Coag-Sense and CoaguChek XS have a troubling gap in results.
I'm hoping that, perhaps with Coagusense, or, worst case, with the FDA, I can get an answer to the question: why are the Coag-Sense results so much lower than the lab or the Coaguchek XS?
So if self-testing once per week (and don't go to the lab), how does one adjust their Warfarin/Coumadin dose if their self-testing INR result comes in at say the bottom of their range and with the history of their machine/strips the lab is usually lower by .2 to .5? Do you go by the results of the machine? Guess what the lab might have been? Or shoot somewhere in the middle? e.g. if trying to maintain a range between 2.5 and 3.5 and self-test reports an INR of 2.5, that might mean a lab might have reported at low as 2.0 (hopefully not lower).
That's been my quandary, too. In the case that you described, if your meter gives you an INR at the bottom of your range -- and you expect that the lab's values will be even lower, you should up your dosage a bit (small changes, not more than, say 1 mg/day) and tweak it up just a bit. It's safer to be more in the middle than it is to be sitting near the bottom. Warfarin has a slow half-life - you won't see the impact of changes you make today for about three days. So, you'll have to be patient to see the results of dosing changes.
Most of the time, labs don't vary by as much as .5.
My real frustration is that I have two meters, both reliably reporting results (the CoaguChek XS nearly agrees with the one at an anticoagulation clinic), and the Coag-Sense machines I use (I have two) give results that are an almost perfect match to each other, but the results of the CoaguChek XS and Coag-Sense may be as much as 1 whole point apart. The CoaguChek XS seems to produce results that are closest to the labs.
In my case, it's kind of a question of 'which should I trust'? What I'm doing now is steering for a dose that would let my Coag-Sense produce a result that is near, but not at, the bottom of the range, and gets a value from the CoaguChek XS that is near the top of the range.
I know that it's probably crazy to be this concerned about it. It's probably even crazier, realizing that an INR of 2.5 on the Coag-Sense may mean labs or CoaguChek XS report a value around 3.5 - because 3.5 really isn't that big a deal, anyway. For myself, my main concern is staying away from the bottom of the range - with either meter. As long as my INR is close to 3.5, I don't worry.
Most of the time, labs don't vary by as much as .5.
My real frustration is that I have two meters, both reliably reporting results (the CoaguChek XS nearly agrees with the one at an anticoagulation clinic), and the Coag-Sense machines I use (I have two) give results that are an almost perfect match to each other, but the results of the CoaguChek XS and Coag-Sense may be as much as 1 whole point apart. The CoaguChek XS seems to produce results that are closest to the labs.
In my case, it's kind of a question of 'which should I trust'? What I'm doing now is steering for a dose that would let my Coag-Sense produce a result that is near, but not at, the bottom of the range, and gets a value from the CoaguChek XS that is near the top of the range.
I know that it's probably crazy to be this concerned about it. It's probably even crazier, realizing that an INR of 2.5 on the Coag-Sense may mean labs or CoaguChek XS report a value around 3.5 - because 3.5 really isn't that big a deal, anyway. For myself, my main concern is staying away from the bottom of the range - with either meter. As long as my INR is close to 3.5, I don't worry.
pellicle
Professional Dingbat, Guru and Merkintologist
so why not use the XS? Its not like the differences between it and labs are actually clinically significant, and that you see a greater variance above INR=4 and below INR=2 is irrelevant when you actually WANT to remain between those values ... is that not the goal?
pellicle
Professional Dingbat, Guru and Merkintologist
like yourself I no longer do labs, I was for some time making 6 monthly comparisons but have not done that in at least a year or two now.
How do you adjust? its quite simple: the reason for taking warfarin is simply and only one thing; to remain in the therapuic range. So if you are under that then you simply need more, if you are over that then you simply need less.
Myself I don't sweat being 3.5 when my range is 2~3 and wait till I see a clear trend. Afterall I'm testing weekly not every 2 months, so I actually can see trends (unlike those poor souls).
There is a rule of thumb that you adjust your dose by around 10% (up or down) to counter a trend and then test again. Myself I also do something like just add or subtract 20% from one dose and then resume the rest of the week on the previous dose. This will result in a brief change and if my situation has altered (which it does from time to time) then it will be high / low on the next reading and I'll probably subtract or add about 10% to my dose for the next week and test again (which happens because I test weekly.
I go into detail on my blog:
http://cjeastwd.blogspot.com/2015/10/managing-my-inr-example.html
http://cjeastwd.blogspot.com/2017/01/2016-inr-data.html
http://cjeastwd.blogspot.com/2014/09/managing-my-inr.html
HTH
Pellicle - I was wondering about that, myself (why not just use the XS?).
In the past, I was so supportive of the Coag-Sense, convinced of its better accuracy than the XS, and had such confidence in the Coag-Sense that I didn't test at all with the XS.
To me, it almost seemed that the hospitals and labs were wrong. I hate to admit it, but as much as Coag-Sense insists that their strips are carefully tested and the reagents tested, and adjustments are printed on the strips to ASSURE absolute accuracy, in the past year or two, the Coag-Sense may have been wrong.
At least, the results for me were out of sync with the labs and hospital.
I recently lost a bit of faith in the Coag-Sense and got some XS strips for comparison testing. The results of the XS more closely correlated with lab and hospital than the Coag-Sense.
For the past two months, I've been running tests comparing the two meters (and a few hospital blood tests), and found that the values start to diverge with an INR of 2.5. At the lowest level, a 2.5 on the XS shows up as a 2.1 on the Coag-Sense. Even if the Coag-Sense is right, as long as the CoaguChek XS gives a result of 2.5 or higher, my INR will be AT LEAST 2.0.
Although I have dozens of Coag-Sense strips - and they'll probably now go unused, and three Coag-Sense meters (two of the old style, one new model), I probably WILL stop using Coag-Sense and use the XS for the bulk of my testing.
I don't have problems managing my INR. It's nearly always in range. I haven't tried the method that you outline - with one reduced dose, and then test for results a few days out.
Instead, I make small changes - usually around 10%, then check in three days or a week. The fluctuations aren't extreme enough to put me in any danger, and my goal is just to stay in range.
Hey - does anyone have some extra XS strips for sale? I'll be needing some n a couple months....
In the past, I was so supportive of the Coag-Sense, convinced of its better accuracy than the XS, and had such confidence in the Coag-Sense that I didn't test at all with the XS.
To me, it almost seemed that the hospitals and labs were wrong. I hate to admit it, but as much as Coag-Sense insists that their strips are carefully tested and the reagents tested, and adjustments are printed on the strips to ASSURE absolute accuracy, in the past year or two, the Coag-Sense may have been wrong.
At least, the results for me were out of sync with the labs and hospital.
I recently lost a bit of faith in the Coag-Sense and got some XS strips for comparison testing. The results of the XS more closely correlated with lab and hospital than the Coag-Sense.
For the past two months, I've been running tests comparing the two meters (and a few hospital blood tests), and found that the values start to diverge with an INR of 2.5. At the lowest level, a 2.5 on the XS shows up as a 2.1 on the Coag-Sense. Even if the Coag-Sense is right, as long as the CoaguChek XS gives a result of 2.5 or higher, my INR will be AT LEAST 2.0.
Although I have dozens of Coag-Sense strips - and they'll probably now go unused, and three Coag-Sense meters (two of the old style, one new model), I probably WILL stop using Coag-Sense and use the XS for the bulk of my testing.
I don't have problems managing my INR. It's nearly always in range. I haven't tried the method that you outline - with one reduced dose, and then test for results a few days out.
Instead, I make small changes - usually around 10%, then check in three days or a week. The fluctuations aren't extreme enough to put me in any danger, and my goal is just to stay in range.
Hey - does anyone have some extra XS strips for sale? I'll be needing some n a couple months....
When I switched providers, they gave me a new meter and the previous firm did not ask for the meter back. When my mother in law died, they did not ask for the meter back. They don't want the risk of using a used meter with a new patient.
If they DO get them back, they probably destroy them.
The non-return policy is probably a major source of meters on eBay.
In terms of the Roche Anticoagulation service, when I spoke to Roche last year, they told me that they DO get the Vantus meters back when a person leaves the service. Presumably, they destroy them. They would apparently prefer to destroy them than to see any entering the Grey Market.
The non-return policy is probably a major source of meters on eBay.
In terms of the Roche Anticoagulation service, when I spoke to Roche last year, they told me that they DO get the Vantus meters back when a person leaves the service. Presumably, they destroy them. They would apparently prefer to destroy them than to see any entering the Grey Market.
BluesCards
Member
So, this will be my first post, but I have been a lurker for over 1 year. Today is my 1 year surgery anniversary for Aortic valve to On-X.
This thread caught my eye as I have been using the Coag-Sense for almost one year to manage my INR. I did two lab draws early on and then compared to my Coag-Sense, was within .1 each time, so to save my arm, I have been doing weekly Coag-Sense checks.
I only have 1 arm for blood draws due to prior cancer treatment in 2010 - too many lymph nodes gone. My veins like to hide and roll courtesy of the Chemo I had, so I was thankful that my doctor allowed me to do home testing. I bought the machine outright and have been happy with it.
This thread though gives me pause if I am making the right decision.
The home service that was offered is very pricy, and part of the reason I bought my own meter.
Is there no one else other that protimenow using this meter?
This thread caught my eye as I have been using the Coag-Sense for almost one year to manage my INR. I did two lab draws early on and then compared to my Coag-Sense, was within .1 each time, so to save my arm, I have been doing weekly Coag-Sense checks.
I only have 1 arm for blood draws due to prior cancer treatment in 2010 - too many lymph nodes gone. My veins like to hide and roll courtesy of the Chemo I had, so I was thankful that my doctor allowed me to do home testing. I bought the machine outright and have been happy with it.
This thread though gives me pause if I am making the right decision.
The home service that was offered is very pricy, and part of the reason I bought my own meter.
Is there no one else other that protimenow using this meter?
Yes, BluesCards. There are others. They just haven't responded to this thread.
Years ago, I went on a quest to find the most accurate meter. Back then, the CoaguChek XS and Coag-Sense were the closest to the labs.
The XS diverged (was higher than) from the labs and the Coag-Sense by an increasing amount the higher INR went up. I chose the Coag-Sense because it either matched the lab, or was slightly lower than the labs. Because I was most concerned about my INR getting below 2.0, and the Coag-Sense would help keep my INR above 2, I chose this one to trust.
I stopped using my XS. I got to a point where I didn't even bother doing blood draws to verify accuracy.
I had a high degree of confidence in the accuracy of the meter. '
Over the past few years, I've had a few blood draws, and even a few blood draws by hospital labs. ALL have been higher, some by almost a full point, than the Coag-Sense, At the time, no red flags went up.
Not any more.
I've asked Coagusense a few times about the reason for the differences. They stand behind the accuracy of their strips.
I've tested with the strips that they sent me. I tested with strips that I bought. All matches provided INRs that matched quite closely.
I ran tests using the old model and the new model, and both matched.
If there WAS an error when compared to labs and XS, the error was consistent. ALL Coag-Sense tests matched each other - regardless of machine or batch of strips.
Curious, I began parallel testing with the XS. There was a difference from the Coag-Sense. I was hospitalized a few times over the past four months, and these results were similarly higher than the Coag-Sense. The XS results were closer to the labs.
I tracked my INR, taken by both meters, as I raised my INR back into range (they lowered it when I was in the hospital). I tracked how the two meters diverged.
I'm not surprised to read that your INR and the labs matched. I've heard this from others, too. I had full faith in my Coag-Sense.
But something's not right for me. Maybe something has changed in my blood or chemistry that doesn't work right with their reagents. I don't know.
It's just somewhat troubling. (Plus - if it happense to ME, I wonder how many others may be getting similarly 'wrong' results).
Years ago, I went on a quest to find the most accurate meter. Back then, the CoaguChek XS and Coag-Sense were the closest to the labs.
The XS diverged (was higher than) from the labs and the Coag-Sense by an increasing amount the higher INR went up. I chose the Coag-Sense because it either matched the lab, or was slightly lower than the labs. Because I was most concerned about my INR getting below 2.0, and the Coag-Sense would help keep my INR above 2, I chose this one to trust.
I stopped using my XS. I got to a point where I didn't even bother doing blood draws to verify accuracy.
I had a high degree of confidence in the accuracy of the meter. '
Over the past few years, I've had a few blood draws, and even a few blood draws by hospital labs. ALL have been higher, some by almost a full point, than the Coag-Sense, At the time, no red flags went up.
Not any more.
I've asked Coagusense a few times about the reason for the differences. They stand behind the accuracy of their strips.
I've tested with the strips that they sent me. I tested with strips that I bought. All matches provided INRs that matched quite closely.
I ran tests using the old model and the new model, and both matched.
If there WAS an error when compared to labs and XS, the error was consistent. ALL Coag-Sense tests matched each other - regardless of machine or batch of strips.
Curious, I began parallel testing with the XS. There was a difference from the Coag-Sense. I was hospitalized a few times over the past four months, and these results were similarly higher than the Coag-Sense. The XS results were closer to the labs.
I tracked my INR, taken by both meters, as I raised my INR back into range (they lowered it when I was in the hospital). I tracked how the two meters diverged.
I'm not surprised to read that your INR and the labs matched. I've heard this from others, too. I had full faith in my Coag-Sense.
But something's not right for me. Maybe something has changed in my blood or chemistry that doesn't work right with their reagents. I don't know.
It's just somewhat troubling. (Plus - if it happense to ME, I wonder how many others may be getting similarly 'wrong' results).
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BluesCards
Member
Thanks for the reply - as I mentioned, I have been lurking for over a year, so I am aware of all your challenges at least during that time. Hope things are getting better!
I pushed my Doctor to allow me to self test, as I did not want to go the lab every week - round trip it was about 1 1/2 hours for something I can do at home in minutes. He agreed, wrote the script and I bought the new Coagu-sense meter. I report my INR every week, and have been stable. I have had to reduce my value three times already for various procedures, and then get it back up. Doctor was aware of all of these, and just wanted to see my INR go back up. With the tips from the forum, I figured out the best way to do it. I did have a few readings around 3.4 to 3.8 so I know I over corrected on the about of warfarin. I can also tell when I am a bit to high as my finger bruises a bit more.
I have a physical coming up and will see if my primary doctor will let me get my INR checked as one of the labs that will get drawn. She may not as she already told me she will not monitor that value. No worries, Doc, my cardio has it.
I am more that curious as to why you values are so far off from each meter. Head scratcher for sure.
I pushed my Doctor to allow me to self test, as I did not want to go the lab every week - round trip it was about 1 1/2 hours for something I can do at home in minutes. He agreed, wrote the script and I bought the new Coagu-sense meter. I report my INR every week, and have been stable. I have had to reduce my value three times already for various procedures, and then get it back up. Doctor was aware of all of these, and just wanted to see my INR go back up. With the tips from the forum, I figured out the best way to do it. I did have a few readings around 3.4 to 3.8 so I know I over corrected on the about of warfarin. I can also tell when I am a bit to high as my finger bruises a bit more.
I have a physical coming up and will see if my primary doctor will let me get my INR checked as one of the labs that will get drawn. She may not as she already told me she will not monitor that value. No worries, Doc, my cardio has it.
I am more that curious as to why you values are so far off from each meter. Head scratcher for sure.
Yes. I'm curious, too. The Coag-Sense is reliable - from strip lot to strip lot, and from meter to meter, and all seem to be reliably 'wrong?'.
Before I go to the FDA about this (if it's happening to me, and dosing is being done based on incorrect readings, wouldn't it be safe to assume that others are having the same issues?) - I would like to see if I can figure this out. So far, the only responses that I got from Coagusense were a) if you know that your INR is one point higher, just add the one point to what the meter tells you, or b) we carefully check all our strips before we send them out and we stand by our results.
In my case, neither are satisfactory answers.
I'll try to contact the manufacturer again, and hope to get a satisfactory resolution to this.
As far as you are concerned - regardless of which meter you use, it's always good to have a blood draw just to see how close the lab's result is to your meter's results. When I had almost absolute faith in my meter's accuracy, I rarely had blood draws. In the last year or so, I've had many more - most were unintentional - hospital admissions, etc.
See if you primary will let you get your blood drawn and tested at a lab - and leave the real job of management to yourself. Just remember not to make large dosing changes - they can trip you up. Also, realize that an INR between 3 and 4 isn't that terrible. And, finally, even if you have to drop your INR below 2, return to your regular dose and your INR should be back in range in just a few days.
Before I go to the FDA about this (if it's happening to me, and dosing is being done based on incorrect readings, wouldn't it be safe to assume that others are having the same issues?) - I would like to see if I can figure this out. So far, the only responses that I got from Coagusense were a) if you know that your INR is one point higher, just add the one point to what the meter tells you, or b) we carefully check all our strips before we send them out and we stand by our results.
In my case, neither are satisfactory answers.
I'll try to contact the manufacturer again, and hope to get a satisfactory resolution to this.
As far as you are concerned - regardless of which meter you use, it's always good to have a blood draw just to see how close the lab's result is to your meter's results. When I had almost absolute faith in my meter's accuracy, I rarely had blood draws. In the last year or so, I've had many more - most were unintentional - hospital admissions, etc.
See if you primary will let you get your blood drawn and tested at a lab - and leave the real job of management to yourself. Just remember not to make large dosing changes - they can trip you up. Also, realize that an INR between 3 and 4 isn't that terrible. And, finally, even if you have to drop your INR below 2, return to your regular dose and your INR should be back in range in just a few days.
BluesCards
Member
Thanks for the feedback Protimenow! I will see what I can go to get a lab draw during my physical. I plan to check at home right before I head in. Thanks again!
I'm glad I could help a bit. INR doesn't usually change very rapidly (unless you've loaded up on greens and waited 12 hours or so to test). Testing a few hours on either side of a blood draw will give you a good value to compare to the lab.
I look forward to seeing your results.
I look forward to seeing your results.
ScribeWithALancet
Well-known member
- Joined
- Oct 27, 2019
- Messages
- 84
If you read my two posts on the first page of this sequence, I have been using the Coag-Sense since approximately Sept of last year. Three years ago, I decided on a meter based on my reactions to what Pellicle and Protime had posted.
My health plan finally signed a contract to provide a meter last year. I went thru the process, they wanted me to rent one (a CoagUChek). I resisted that because they could provide me no written documentation for the contract. I got a prescription and purchased a CougSense - the new model. It took me several months to get used to it. I am a retired operations research engineer and once I was comfortable, I started systematically going thru the dosing to move me from the bottom of my "safe" range (2.0 to 4.0) to the top by 0.5 increments in my dosing. I did the increments every two weeks. I got 7 tests done. Each test was a paired Lab Test INR with a CoagSense INR. I did the CoagSense Prick within 30 minutes of the Laboratory Blood Draw. I had read studies done by Stacy A. Johnson, MD and Sara Vazquez, PharmD on the general topic of Point-of-Care or Clinical Lab INR for AntiCoagulation Monitoring. It was fairly straightforward to apply their statistical methods to compare my Health Plan's Laboratory INR testing to the CoagSense. Dr. Johnson warned me to look out for variations in the test strip and Laboratory Based Reagents and to look out that the Lab did not shift what machine they were using for the testing. After 7 paired tests the virus struck and forced me to rely on the CoagSense exclusively. However, by that time, I could predict the Health Plan INR within plus minus 0.1 to 0.2 100% of the time. This applied for the range 2.4 to 3.7. With regression analysis, one cannot make accurate predictions outside of the data range. However, by making minor adjustments to my dosage of 0.25 or 0.5, I can generally stay between 2.8 and 3.2 on my meter. I have only been out of range twice since the epidemic. Once was because of taking too much Tylenol (INR too high). The other time was because I did not warm my hand properly and got a barely adequate drop of blood (INR too low). Both times my INR came back into range after three days.
The references that I relied on for developing this approach, beyond those listed by Pellicle and Protime are:
1) Van Geest-Daalderop, J.H., Pequeriaux, N.C., & van den Besselaar, A.M. (2009). Variability of INR in patients on stable long-term treatment with phenprocoumon and acenocoumarol and implications for analytical quality requirements. Thromb Haemost 102, 588-592.
2) “Correction factor to improve agreement between point-of-care and laboratory International Normalized Ratio values”, American Journal of Health-System Pharmacy, Volume 74, Issue 1, 1 January 2017, Pages e24–
e31, https://doi.org/10.2146/ajhp150813
3) “Comparison of two point-of-care international normalized ratio devices and laboratory method”Sara R. Vazqueza, Ryan P. Fleminga and Stacy A. Johnson, 2017 March 15 abstract available from: Comparison of Two Point-Of-Care International Normalized Ratio Devices and Laboratory Method - PubMed
4) “Point-of-Care or Clinical Lab INR for Anticoagulation Monitoring: Which to Believe?”Stacy A. Johnson, 2017 April 01 article available from American Association for Clinical Chemistry (AAAC) Clinical Laboratory News Page Not Found | AACC.org /point-of-care-or-clinical-lab-inr-for-anticoagulation- monitoring-which-to-believe
5) Roche Diagnostics GmbH. (2006). CoaguChek® XS Evaluation Study (internal reference). Cited at: http://www.coaguchek.ro/content/dam/internet/
dia/coaguchek/coaguchek_ro/coaguchek_patient/pdf/CoaguChek_accuracy- precision_Bro_12pg_RO.pdf
6) “Preanalytical variability: the dark side of the moon in laboratory testing”, Lippi G, Guidi GC, Mattiuzzi C, Plebani M.. Clin Chem Lab
Med. 2006;44:358–65.http://dx.doi.org/10.1515/CCLM.2006.073. [PubMed] Preanalytical Variability: The Dark Side of the Moon in Laboratory Testing - PubMed
7) “Preanalytical variables and off-site blood collection: influences on the results of the prothrombin time/international normalized ratio test and implications for monitoring of oral anticoagulant therapy” van Geest- Daalderop JH, Mulder AB, Boonman-de Winter LJ, et al. . Clin
Chem 2005;51:561-8. 10.1373/clinchem.2004.043174 [PubMed] Preanalytical Variables and Off-Site Blood Collection: Influences on the Results of the Prothrombin time/international Normalized Ratio Test and Implications for Monitoring of Oral Anticoagulant Therapy - PubMed [CrossRef] [Google Scholar]
The regression equation I developed was Y=0.9646x + 0.0606. This had a Rsquare of 0.92 which is supposed to be very good. What was particularly interesting to me was that I found that the standards for Lab testing allowed a 10% drop in ink for a 6 hour lag between blood draw and test resulting. Applying this to create a "corrected" INR result had the CoagSense meter in 3 of the 7 data pairs within 0.2 of the Lab and in 4 of the 7 tests with 0.1 of the lab. My conclusion is that, for the reagents on the strips from CoagSense and the reagents used by MY health plan lab, there is no real difference.
If you plot the predicted (from the regression equation and the CoagSense) lab values versus the actual lab values. they overlap closely. Similarly, if you plot the corrected lab values with the CoagSense values, they overlap closely.
I am totally comfortable with my meter. I use a thermophore heating kit to warm my hand for 3-4 minutes prior to the blood draw.
However, you need to develop your own regression equations, you would need to find a Laboratory that consistently uses the same Laboratory machine and reagent and then run a series of tests across the low to high end of your recommended range and probably 0.5 above and below it in the generally safe range (Pellicle posted a chart that shows that 2.0 to 2.5 and 3.5 to 4 are general safe) or the very safe range 2.5 to 3.5 for my St. Jude mitral valve.
After the epidemic is over (hopefully by the mid-Fall? ) you can do your own paired testing. If you are good at tracking numbers, Microsoft Excel and Apple Numbers both give the same regression equation answers. I plotted them one time in Libre Office / Open Office and got the same answers.
I believe you are making the right decision to use the CoagSense. However, you need to prove it to yourself by running through the math.
I have the advantage that my health plan has its own laboratories and sends all INR test blood to be tested on the same machine. They let me use the same phlebotomist each time (she is very good and leaves no blood or bruises ! - ) Thus, making the paired tests, for me, is much easier then it is for some.
Walk in His Peace,
Scribe With a Stylus
ScribeWithALancet
Well-known member
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Protime,
The Lot # for the test strips I used to pair my data with the Health Plan Lab was 200061. They were barcoded 50130371.
Walk in His Peace,
Scribe With a Stylus
ScribeWithALancet
Well-known member
- Joined
- Oct 27, 2019
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- 84
MdaPA
You mentioned "compared to the lab (Quest)"
Quest is a big enough organization that it may have more then one machine in more then one location and they may use more then one reagent on their different machines.
Roche did a study where they demonstrated that different laboratory INR machines with different reagents may vary +-0.5 in their INR results from the same sample of blood. They made the observation that this difference was basically the same as the variation of any individual machine from their CoagUChek device. Pellicle posted this table at one point and it was a fascinating look into why INR is an art and not a physics science.
My wife reminded me that I found out that lag times between when the lab does the blood draw and when the do the Resulting of the test can cause drops in the INR from the Lab Machine of up to 10%. If they switched which machine they are sending the blood to, they may have also changed the delay time in processing the blood.
In addition to the vitamin C, you need to find out which machine they are using for your wife's blood, what reagents they are using and where it is located. Read Dr. Stacy Johnson's research results on INR vs device testing. (He likes the CoaguChek XS for his patients as they find it easier to use. I prefer the CoagSense and find it easy to use, but I am a retired engineer so that may bias me in favor of mechanical gadgets ; - ).
Walk in His Peace,
Scribe With a Stylus
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ScribeWithALancet,
I will inquire further at the lab (Quest) if they can identify what reagent and machine they use from test-to-test to see if there is pattern to the discrepancies.
I will inquire further at the lab (Quest) if they can identify what reagent and machine they use from test-to-test to see if there is pattern to the discrepancies.
That's a great point! All this time I have been thinking if both blood draws from self-test and the lab were as close as possible (say under 1 hour) that that would have made for a good comparison, not introduce another variable. I was not thinking about the delay from the time the blood was drawn to the time the lab actually performed the test (not even sure the lab site does the testing, they might even send it out?). All good questions I'm going to inquire about.
ScribeWithALancet/BluesCards,
Where did you buy the meters from with your scripts? Roche? And you did so without their reporting service and fees? My wife's out-of-pocket for their service is $101/month.
And where do you get your strips from? ebay?
