New Coag-Sense meter

[Gustav]

Has anyone tried a back to back test with your lab. I always tend to get a .3-.4 variance on my lab result compared to my CoaguCheck XS strips, Lab always being lower. So if im aiming for 2.0 in reuslt I aim for a 2.4 readout on the XS. Then again one would ask whether the lab result is the correct one or not. Any insight ?

 

[Protimenow]

I've done it for years. Not exactly back to back - usually within an hour or two of the lab.
A few years ago, I was evaluating meters against each other and against the labs. There were a lot of back to back and, I guess, side to side, tests across meters and with labs.

Two weeks ago, my rheumatologist's lab said my INR was 5.2. A few days earlier, my machine gave me 2.8. I knew that the lab was wrong, but I wanted to make the proof incontrovertible:

I tested with two Coag-Sense meters - my new PS2, and the 'classic' version, and the results were within .2 of each other. I got a blood draw at my PCP an hour later, and two hours after that, I got a blood draw at a UCLA clinic.

The labs were a bit higher - but within .1 of each other.

In the past, I've compared blood draws to meter results - in some cases the prothrombin times were identical (or practically identical), but the INRs didn't match -- the value for the reagent used by the lab was different from the ones on the strips.

In the past, I would get a 'back to back' test at the labs monthly - the the results were always close. Now, it's every six months or so, or when I see a doctor who runs an INR test.

 

[Chris]

Has anyone tried a back to back test with your lab. I always tend to get a .3-.4 variance on my lab result compared to my CoaguCheck XS strips, Lab always being lower. So if im aiming for 2.0 in reuslt I aim for a 2.4 readout on the XS. Then again one would ask whether the lab result is the correct one or not. Any insight ?

I'm 'doing one now'. I just had a blood draw at the lab, drove home and ran a test with my PT2. There was a thirty minute difference from when the lab drew my blood and my own test.
My meter shows my INR to be 2.2. I probably won't get the lab results until tomorrow morning.

 

[Keithl]

So I emailed CoagSense just to get their take on my findings and here is what they said ;


Systems will rarely match exactly but should correlate. There will be a natural bias that exists between two systems but as long as that bias falls within the WHO and ISO Guidelines for what is considered an acceptable bias there should not be a patient management issue. The values you presented would fall within the acceptable bias range. The difference in technology, thromboplastin and ISI plays a role in contributing towards an inherent bias, and as long as a patient is managed with one system, that is fine. Below are the ISO guidelines for acceptable bias.

. In the INR range below 2.0, 90% of the allowable differences between results from the POC system and reference system shall be ±0.5.
. In the INR range of 2.0 to 4.5, 90% of the allowable differences between results from the POC system and reference system shall be ±30%.
. In the INR range of 4.6 to 6.0, no performance criteria are listed for INR values.
WHO Technical Report Series 889, WHO Expert Committee on Biological Standardization, Forty-eighth report. Section 6.1.1 The Calibration procedure, Calibration of a secondary standard, Blood Samples.Section 7 The use of calibrated thromboplastins in clinical practice.
(ISO/DIS 17593) ISO Draft of 2004, titled "Clinical Laboratory Testing and In Vitro Diagnostic Test Systems-In Vitro Monitoring Systems for Anticoagulant Therapy Self Testing".

The Roche unit tends to run a bit higher. In fact, more recently they have had high INR issues which have resulted in a recall

https://www.fda.gov/medical-devices...t-test-strips-due-inaccurate-inr-test-results
We are still noticing that the Roche system is running higher even with post recall lots of strips.

Again, we recommend only managing your therapy with the Coag-Sense system.

 

[Keithl]

If I am doing my math correctly then in the 2.0 - 3.0 range the margin of error allowable is 1.4 - 3.9? Or since the low end falls below 2.0 would it be 1.9 - 3.9, to still be reported in the 2.0 - 3.0 range? essentially a -0.1 on the low end to up to +0.3 on as you scale up through the 2-3 range. That seems to fall nicely into what I am seeing with the comparison as the differences range .2 - .3 higher for the Roche. with it being .2 higher when I am in the mid 2s and then .3 higher as I get around 3.0.

 

[Keithl]

Has anyone tried a back to back test with your lab. I always tend to get a .3-.4 variance on my lab result compared to my CoaguCheck XS strips, Lab always being lower. So if im aiming for 2.0 in reuslt I aim for a 2.4 readout on the XS. Then again one would ask whether the lab result is the correct one or not. Any insight ?

I am doing it Friday, will do meter check while fasting for a normal blood labs and asking for an INR as well.

 

[Protimenow]

There's no need to fast when getting your INR tested. You fast for a blood glucose test, but the INR test has nothing to do with this. Further, even if you eat a LOT of greens before your test, any effects won't show up in your INR until at least 12 hours later.

If you're having some tests done that require fasting, you should, of course, fast; but you don't need to fast for an INR test.

---

Gustav - I've used the XS before, and compared it to labs and to other meters. I would not be comfortable with a 2.0 coming from an XS -- the results on an XS are often higher than lab results. Your question about wanting a 2.4 result from the XS makes sense to me -- having an INR into the 3s isn't much of a problem, so I'd personally aim even higher than 2.4 on an XS. (FWIW - I'm comfortable with a 2.0 on my Coag-Sense, because the result is usually at, or below the lab results - meaning that my INR is probably AT LEAST 2.0. Even with a 2.0 on a Coag-Sense, I'd probably try to raise my INR slightly, because tickling 2.0 is a concern to me, and 2.5 -3.0 isn't that big an issue).

 

[Keithl]

I am not fasting for the INR I get periodic full blood work with complete advanced lipid profile, usually every 6 months, happens to be time so will have them pull an INR as well.

 

[Warrick]

Hoping Im not telling people how to suck eggs but with the XS I have found its the little things that make a sucessful test because error 5 is s**t.
Put the blood drop on the side of the strip rather than trying to dab it in the center, the capillary action really works well and even on previously doubtful drop sizes I get a good test.
If its cold I run my hands under warm water for a bit until theres good colour and then test once dried.
Remember 180 seconds is 3 minutes so is longer than you think at the time... dont panic.

I was also told that if you are running out of time just turn the machine off, dont touch the strip at all and then turn it back on when ready, I have done this once a year or so ago and it did work, so if u are going to waste a strip anyway then try it, I cant quite remember but I think it goes thru the warm up and gives you another 180 seconds.

Failing that panic and stab multiple fingers until u get a good drop... I use to but once u get it down packed its no worries

 

[pellicle]

Failing that panic and stab multiple fingers until u get a good drop... I use to but once u get it down packed its no worries

 

[Chris]

I'm 'doing one now'. I just had a blood draw at the lab, drove home and ran a test with my PT2. There was a thirty minute difference from when the lab drew my blood and my own test.
My meter shows my INR to be 2.2. I probably won't get the lab results until tomorrow morning.

The lab said my INR was 1.9.

 

[Protimenow]

Warrick: Yes, the drop of blood on the side of the strip is the easiest way to go with the XS. When I was testing with the XS (and other meters), this is the method that I also used.

My understanding about the XS strips is that they shouldn't be exposed to air for very long - the electrical sensors on the strip are affected by the air or humidity or something else in the air- which is the reason that they come in a sealed tube, and you're instructed to put the cap back on as soon as possible. I would be a bit concerned if you turn the machine on, then off with the unused strip still in the meter. Although the meter doesn't know that the strip has been left exposed to air, I'd wonder if something has changed on the strip to create a false INR value.

Pellicle posted some material about how to obtain a good drop of blood for testing. (I've found that testing after I shave gets me a good drop - the combination of exposure to warm water and arm movements involved in shaving - even though most of the work is done by the arm that I don't use for testing - seems to make the blood supply in my hand pretty strong.

Chris - I'm a bit surprised that the PT2 gave you a value that was higher than the lab result. Depending on which valve you have, you might re-test or consider a minor dosage increase - but, of course, if you an find a professional who has any clue how to manage anticoagulants, you can check with him/her before making a minor change. And, of course, both values are within the WHO prescribed amount of error. (Still, I'd trust the PT2 before trusting the lab - Coag-Sense has a lot more to lose if their reagent values are wrong).

 

[Chris]

Chris - I'm a bit surprised that the PT2 gave you a value that was higher than the lab result. Depending on which valve you have, you might re-test or consider a minor dosage increase - but, of course, if you an find a professional who has any clue how to manage anticoagulants, you can check with him/her before making a minor change. And, of course, both values are within the WHO prescribed amount of error. (Still, I'd trust the PT2 before trusting the lab - Coag-Sense has a lot more to lose if their reagent values are wrong).

Yes, when the Medication Management folks called me with the results, they recommended that instead of my current 3mg/day, that I take 4mg twice a week and 3mg the other five days. I can math, so I asked if they really thought that would be enough of an increase (and isn't it better to take the same dose every day?). Someone farther up their food chain called me back a few hours later and told me to up my dose to 4mg x days/week and 3mg on the other three days. That sounded better and then I said that since that was relatively close to 3.5mg/day, couldn't we get me a prescription for some pills that were easily divided into that number. They're putting in for 1mg pills so that I can easily take 3.5mg/day.
I'm not completely convinced that will be enough, but at least we're moving in the correct direction.

When I self-tested and saw my INR was low, I took it upon myself to take 4mg that day (Monday) and the nurse I spoke to yesterday (the one that upped me to 3.5/day) had me take another 4mg yesterday. I'll take 3.5mg today. Next blood draw is scheduled for Monday, but I'll self-test before that.

 

[pellicle]

Pellicle posted some material about how to obtain a good drop of blood for testing.

thanks for the plug


Lance the side and apply to the edge of the strip.

Note that the finger turns red when "wrapped" ... if it doesn't it means its not going to give you any blood. So I'd test this with another finger before starting the count down
(Assuming that Protime shaves after a shower) I'd say that my experience in winter is to sample after my shower in the now warmed bathroom (after I'm dried and clothed).
;-)

 

[LondonAndy]

Agreed. It's harder to waste a strip with the Coag-Sense because, unless you put blood or another lilquid into the well on the strip, the strip remains usable. Although the Coag-Sense meter has a timer on it, you can ignore that and continue using the strip until you DO put blood onto the strip. And, because the blood is drawn into a transfer tube, you know whether or not you have enough blood. (As you know, once you put a CoaguChek XS strip into the meter, you've got a limited amount of time to get the blood onto it ...

This is true, but the time limit is 3 minutes. On the occasions that I have realised a finger prick is not going to yield sufficient blood for a test there has been sufficient time to prick a different finger and try again whilst the strip is still 'live'. I wasted the odd strip when I first started testing but as this is something we do weekly it doesn't take long to get the necessary experience.

 

[Protimenow]

As long as you don't get blood or othe liquid onto the Coag-Sense strip, it's still usable. You may even be able to put the unused strip into a ziploc bag and use the strip for a test later - possibly as long as a week or so later. But, as you noted, it doesn't take long to get the experience necessary to do a perfect test. (Coag-Sense's three minute limit is probably there to save the meter's batteries - while it's waiting to run a test, the meter spins the wheel imbedded in the strip, and an LED is shining through the strip - the strip is still usable until blood is applied).

Pellicle - I frequently don't even have to shave to get a good droplet. Sometimes, I'll rinse my hand in warm water, to warm the capillaries in my hand. Sometimes, this isn't even necessary.

While my strip is warming in the meter, I squeeze my finger, just below the first knuckle (assuming that I'm counting from the fingertip back towards the hand), and the fingertip gets red. There's enough pressure in the fingertip to deliver an adequate droplet. The transfer tubes that come with the strips draw blood into the tube, to the point where it stops. Then, I just put the tube into the well on the strip and push the plunger.

If I was testing with the Coag-Chek XS, I'd use the same method to get the drop, and touch my finger to the side of the strip. (Of course, Pellicle's instructions are helpful for any meter. I used to have a small container of dental floss specifically for constricting blood flow in order to get a good drop of blood).

 

[Keithl]

So I did a CoagSense test Friday and then within 2 hours had lab pull blood as part of my normal labs. Won't have the lab results back for a few days, but I was fasting so the odds of a difference in 2 hours is very slim.


SO over the last 2-3 weeks I have done some occasional compares with my CoagSense and the CoagCheck XS back to back. Here are the comparisons;
(CS = CoagSense XS = CoagCheck)
6/19 CS 2.8 vs XS 3.1
6/22 CS 2.9 vs. XS 3.1
6/30 CS 3.0 vs. XS 3.3
7/7 CS 3.1 vs. XS 3.5

Seems the higher the INR the spread goes up a bit, but seems to be around .2-.4 higher on the XS. I am lowering my dose to get me closer to 2.5 on the CS and test twice a week on the CS, will try another comparison in about 1-2 weeks.

 

[Protimenow]

This variance looks pretty consistent with my testing a few years ago. Both are within an acceptable range of each other. In my earlier testing, I often found that the lab results were almost an average of the results of the two meters.

Personally, I prefer a result slightly lower than labs -- but I've mentioned this dozens of times before.

I'm glad to see testing that compares both meters -- it saves me the hassle and expense of getting some XS strips for comparison testing.

 

[Chris]

So now I have the second lab result to compare to my CS PT2. The first one was Lab = 1.9, CS PT2 = 2.2.
This second on is Lab = 2.5, CS PT2 = 2.7, so it seems the meter is reading a bit high compared to the lab I go to.

fwiw,
Chris

 

[Keithl]

Wow, would be interested in how it compares to mine and then a Coagcheck XS.