Has anyone compared home testing with lab test for accuracy?

[DachsieMom]

So I have started home testing through Coagucheck's service...not 100 percent successfully! The last test, it took me 5 strips! In any event, my level was 3.9. Because my body seems to do the opposite of intuitive (went up after medicine decreased), I decided to lab test upon my doctor's recommendation. About 3.5 hours later, I went for a blood draw. Results are 3.4. Is that a normal margin of error between lab and home test? I think next week, I may take my meter to the lab for real-time comparison.

 

[dick0236]

It can happen. When you say a "blood draw" at your docs office do you mean a finger stick with his machine or a vein draw that is sent out to a lab. If it is a finger stick at your docs office what brand machine does he use. If it was sent to a lab how much time elapsed before the test was run. 3.5 hours between testing at home and then at your docs office can produce different results.......etc., etc. I've had similar discrepancies in the past and could not figure why. It is all part of the learning curve.....so don't give up on self-testing.

 

[pellicle]

Hi

I normally test and compare to a lab about every 6 months. I write this down and date it. I always test the same day as the lab draw and put that column in when I get the info back. Typically now I'm within 0.2 INR units. Sometimes under sometimes over.

But it wasn't always so. When I started I goofed up a lot and was sometimes 1 INR unit out. I wasted strips due to not enough blood. This is what led me Tony current method. Are you trying my method?

 

[Freddie]

I've been comparing the lab results with my Coagucheck XS for about three years and the difference has been .2 higher or lower sometimes .3. Keep in mind (at least in Canada) the lab is allowed a variance of .2 when doing the testing, which involves 3 tests and takes an average.

I would suggest that you become more comfortable with the monitor before taking it to lab to avoid wasting any strips.

 

[bocco]

I used to use an Alere Inratio2 until Kaiser (my insurance) decided they were not accurate. Once evey couple of months I did a home test and then went straight to a vein draw that is sent out to a lab. It was consistently within 0.2 or better. I will be getting a coagucheck next week and I plan to do the same drill.

 

[MethodAir]

There was a small, reasonable variance when comparing Coaguchek with lab results, doctor was ok with it.

 

[yotphix]

My docs require me to get a vein draw every six months for prescription renewal. I actually bring the machine in and test within minutes of the vein draw. The results are normally within .2 in one direction or the other. The one time that my meter showed I was in range (2.8), and the draw did not (3.9), I strongly suspect that it was a failure of the lab, since a test the following day showed them back together again. in range.

 

[T in YVR]

My variance in lab blood draw vs. Coaguchek is small - 0.1 or sometimes the same.

 

[bocco]

Just went in today for a training class on the Coagucheck XS.I tested 4.0 twice during training. So I headed to the lab for a blood draw. I'll post the results for comparison. They already advised me to skip tomorrows dose.

 

[RobThatsMe]

My results are within .2 of the vein draw at the lab. I compare results every 6 months, and always take my unit with me to the lab to test within minutes of the lab draw.

 

[bocco]

Well my vein draw came back at 2.9 yesterday at 12:30pm. 1.5 hours after the self test at 4.0. So I tried another self test this morning early and got 3.7. So yesterday I was thinking that the anibiotics that I took before getting my teeth cleaned 2 days ago had something to do with. Now I'm not sure if my coagucheck is accurate.

 

[dick0236]

Well my vein draw came back at 2.9 yesterday at 12:30pm. 1.5 hours after the self test at 4.0. So I tried another self test this morning early and got 3.7. So yesterday I was thinking that the anibiotics that I took before getting my teeth cleaned 2 days ago had something to do with. Now I'm not sure if my coagucheck is accurate.

Take an INR of your spouse or a friend. If you get an INR around 1.0 your machine is OK. There should not be that much difference, from 2.9 to 4.0 in 1.5 hours.......but don't automatically assume your meter is bad.....it could be the lab.

 

[pellicle]

Hi

Well my vein draw came back at 2.9 yesterday at 12:30pm. 1.5 hours after the self test at 4.0. So I tried another self test this morning early and got 3.7.

that's good .. this demonstrates consistency between stip measurements and 0.3 change over a day is entirely possible.

So yesterday I was thinking that the anibiotics that I took before getting my teeth cleaned 2 days ago had something to do with. Now I'm not sure if my coagucheck is accurate.

I doubt that your antibiotic cover has had such a profound influence on your INR, but even if it was the antibiotic, as it was a one off dose , do not adjust your dose because of it. It will soon flush out of your system.

Like Dick suggests, test it on someone ... that will be definitive.
Note dicks earlier post to you

​

It might.....but maybe not? I am currently having some dental work done and have taken 2000mg amox twice in Aug '15. Below are my INRs over that time:
8/5....3.5
8/12..3.0
8/19..3.7
8/26..3.8
.

Note he is not worried about being nearly exactly your INR? If your INR is between 2.5 and 4 do not adjust dose. You are in an entirely safe range (refer to my previous diagram here and please take a moment to read the axes or ask for help interpreting it if you aren't sure what it meant).

The most common reason people have unstable INR is because of irregular doses and fooling with it. So don't drop you dose as advised (and ask yourself if they are on warfarin and if they may make brainless experiencless text book calls just because its not them).

Wait and see.

I would also consider (as Dick mentioned earlier) that the lab could be the one that is out.

My own INR varies about as you've seen in graphs I've published before. Its not important exactly where it is as long as its between 2 and 4.5 ... of course one may choose to try to keep it on a tightrope of 2.5 but you will not achieve driving a straight line by yanking the wheel left and right.

 

[Julian]

I have tested lab versus my inratio and have noticed the inratio consistently tests 0.5 higher than the lab results for me.

 

[Julian]

Big correction to my above post. I test with a coaguchek unit not an inratio unit. I just came home from gallbladder surgery and I think the pain meds are getting the best of me.

Again, I tested lab versus at home with a coaguchek unit which I've found the coaguchek unit has consistently tested 0.5 higher than the lab results.

 

[LondonAndy]

I go to my hospital's anticoagulation clinic once every 6 months for a check on my Coaguchek results, and difference has been +/- 0.1 mostly, once a difference of 0.2. They mostly check against their version of the Coagucheck machine, but when I dropped out of range a lab test comparison was 0.2 different. So I feel confident self testing is sufficiently accurate to stay in range, and of course the ability to do a finger-prick test more frequently, or when diet changes/on holiday etc, is a joy and much more convenient than having to go to a clinic for a blood draw.

 

[carolinemc]

Boco, you have to realize now that when you are antibotics, it can either lower or up your inr results, no matter the method. You have to give the Antibotics several days to get out of your system before you can get an accurate reading. Try it again after you are done with the Antibotics. A fews can make a difference on the INR results. Hugs for today.

 

[bocco]

OK. Retested today. Used my wife as a baseline. She tested 1.0 with the coagucheck. Then I tested 3.6. High again. Left the house and went straight to the lab for a blood draw. That just came back at 2.9.

So now it looks like the meter tested my wife correctly but was off by .7 when testing me. Not sure what to make of this. We'll see what my guy at the clinic says about all of this.

Also I opened a new package of strips but they were from the same lot.

 

[dick0236]

OK. Retested today. Used my wife as a baseline. She tested 1.0 with the coagucheck. Then I tested 3.6. High again. Left the house and went straight to the lab for a blood draw. That just came back at 2.9.

So now it looks like the meter tested my wife correctly but was off by .7 when testing me. Not sure what to make of this. We'll see what my guy at the clinic says about all of this.

Also I opened a new package of strips but they were from the same lot.

Your meter is testing blood samples. It didn't know that one sample was from your wife and one from you. If she tested 1.0 your meter is reading correctly. Could it be that the lab is off by .7? It'll be interesting to hear the lab techs explanation. I would expect some difference but 20% ???

 

[bocco]

Your meter is testing blood samples. It didn't know that one sample was from your wife and one from you. If she tested 1.0 your meter is reading correctly. Could it be that the lab is off by .7? It'll be interesting to hear the lab techs explanation. I would expect some difference but 20% ???

I agree completely. But this is similar results to what I got 2 weeks ago. Not sure if the lab would be that far off 2 weeks in a row. Also I am usually pretty stable and in range with the dose I'm taking.

I will report back after I hear back from my guy at the clinic.