CoaguChek error 8

[user 16827]

Thought i would share my experience today with my Clinic

I self test once per week.

My machine for a while has been showing error 8 , a restart usually sorts it out
Today i was given a replacement machine at my Doctors.

My machine showed INR 2.6
New machine 2.8
Doctor's calibrated machine 3.0

I was advised that UK best practice allows a 0.5 variation in the machines, if i were to have a Lab venous draw they allow 15%

the test were done within minutes of each other using 3 different finger draws


I was surprised at the tolerances allowed but at least i have learned something.

 

[pellicle]

Hi

interesting story ...

My machine for a while has been showing error 8 , a restart usually sorts it out
Today i was given a replacement machine at my Doctors.

My machine showed INR 2.6
New machine 2.8
Doctor's calibrated machine 3.0

For those reading here are the manual mentions of error message 8 (well and 9 for good measure)

I agree with the views of errors margins allowed in the UK and is the reason I strongly advocate target INR not "oh I'm within my range" when your range may be 2 ~ 3 and you're on 2 ... exactly stuff like this is why you don't want to sit on the margins.

To me its like Tennis, return to the middle of the court as soon as practicable.

Some other information you may find helpful is:

There is an important concept called "clinically significant" in interpreting readings. So a INR variance of 0.2 is not clinically significant, thus 0.4 would be on the margins but no action would normally be taken. Thus 2.6 vs 2.8 is not a clinically significant variance. Perhaps (taking an analytical approach it is wrong to assume that the 3.0 is actually bang on (and indeed this is always a rubbery measurement anyway) in which case we could equally assume 2.6 to be correct and the obtained readings are within +- 0.2

Its always going to be the case that there are minor differences between batches and between measurement systems. Even "blood draws" depending on reagent and lab compliance with "baseline" setting will yeild differences. This is an interesting section from a Roche Publication:

In testing we see that the errors become smaller as INR decreases as in this test publication:

None the less its a good topic to bring up as while its been discussed here many times, not everyone digs through the archives.

Best Wishes

 

[pellicle]

An old post of mine from here which covers this topic a bit:
http://www.valvereplacement.org/for...ot-reading-inrs-correctly?p=849087#post849087

 

[user 16827]

I agree with the views of errors margins allowed in the UK and is the reason I strongly advocate target INR not "oh I'm within my range" when your range may be 2 ~ 3 and you're on 2 ... exactly stuff like this is why you don't want to sit on the margins.

Hi Pell , i have never thought about it that way but it makes perfect sense

Thanks for the extra info, it's very useful to know this stuff

 

[Dodger Fan]

Every time I get a blood draw, I also use my Coaguchek. The blood draw is usually .2 to .3 lower than my meter. I decided a while back to report .3 lower than what the meter says because I know that if I report a 2.0, I am in reality a 1.7 and they won't change my dose (range is 2.0 to 3.0). I could make my own dosing decisions, but I prefer to let them do it for me. I have been self testing since March of 2016.

 

[Protimenow]

Dodger Fan -- In a more recent thread, I asked why you would report a lower than meter value to your INR manager. I'm assuming that they don't already know that these meters report .2 to .3 higher than the labs. Your reasoning for reporting lower results sort of makes sense, as long as the manager doesn't also do this. So - if the meter says 2.0, and you tell your manager it's 1.7, and the manager concludes that it's actually 1.4 - their decision may be a bit more extreme than expected.

FWIW - I use the Coag-Sense, which often reports slightly lower than the labs for a similar reason to your logic. For me, I'd prefer a meter that reports slightly low - if my meter gives me a 2.0, I'm fairly comfortable in the belief that a lab result would be 2.3 or so, and put me at the low end of my range. A 2.0 on a CoaguChek XS would concern me.

 

[LondonAndy]

I decided a while back to report .3 lower than what the meter says because I know that if I report a 2.0, I am in reality a 1.7 and they won't change my dose (range is 2.0 to 3.0).

I self-test weekly, and adjust my own dose when needed. I give the result to my anticoagulation clinic every 6 to 8 weeks, which is whenever they ask for it, and I always give them the exact same figure as shown on the meter. This is because if ever I have something serious happen and need to go into hospital, I think trust in my self-management would be lost if they found different readings to those I have provided. This may be an unlikely situation, but as I ended up with a pacemaker that will need replacing every 7 to 10 years or so perhaps there will be occasion for a comparison to be needed.

 

[Protimenow]

If the hospitals weren't making so much money on the labs, I wouldn't be surprised if they used a meter, too -- and charged $50 to read the result and another $50 or so to analyze it.

 

[pellicle]

If the hospitals weren't making so much money on the labs, I wouldn't be surprised if they used a meter, too -- and charged $50 to read the result and another $50 or so to analyze it.

in australia they often do use a Coagucheck ... in fact its where I was first exposed to the idea (back in the ward after ICU after my 2011 OHS).

Of course being Australia I'm not charged $50 for that ...

 

[Protimenow]

Yes. Enlightened medical systems do things like that for their people.

I saw my first INR meter - a Protime - in 2006. I finally was able to get one in 2009, when I started self-testing. (It was a person's grandmother's meter, and he made me a gift of it. I had a doctor friend order the strips. I've been self-testing for more than a decade).

 

[tom in MO]

In the US, Medicare covers home testing as do private insurance policies. It's cheaper to home test than deal with the expenses of being out of range.

 

[Protimenow]

I can see expenses when you're out of range (below range - long enough, you can have a stroke) (you'll probably know you're above range because of excessive bruising or, perhaps, even blood in the urine). Strokes are expensive - and could be life ending; excessive bleeding is easier to control with Vitamin K -- probably not as expensive.

It's definitely cheaper to home test than it is to deal with the below range consequences.

I may have to see what Medicare will do for me - although I already have meters.

 

[tom in MO]

I can see expenses when you're out of range (below range - long enough, you can have a stroke) (you'll probably know you're above range because of excessive bruising or, perhaps, even blood in the urine). Strokes are expensive - and could be life ending; excessive bleeding is easier to control with Vitamin K -- probably not as expensive.

It's definitely cheaper to home test than it is to deal with the below range consequences.

I may have to see what Medicare will do for me - although I already have meters.

From Wiki: Medicare coverage for home testing of INR has been expanded in order to allow more people access to home testing of INR in the US. The release on 19 March 2008 said, "[t]he Centers for Medicare & Medicaid Services (CMS) expanded Medicare coverage for home blood testing of prothrombin time (PT) International Normalized Ratio (INR) to include beneficiaries who are using the drug warfarin, an anticoagulant (blood thinner) medication, for chronic atrial fibrillation or venous thromboembolism." In addition, "[t]hose Medicare beneficiaries and their physicians managing conditions related to chronic atrial fibrillation or venous thromboembolism will benefit greatly through the use of the home test."

 

[Superman]

I’ve always wondered about timing and the impact. I believe you need to provide a sample within 15 seconds of the finger stick.

So if you get there in 3 seconds vs 15 seconds, wouldn’t your test result vary? Taking three tests that close together, did you get your sample to the machine in the exact same amount of time? Or is that an insignificant impact on outcomes?

It appears the manufacturer believes waiting longer than 15 seconds from the stick would have enough of a material impact to make the result useless.

 

[Protimenow]

The reasoning here, as I understand it, is that the blood will start to clot within fifteen seconds, throwing the value off.

I'm not sure about what happens between the time of incision, and the time fifteen seconds after incision.

It could be that any change in clotting activity between second 0 and second 15 would affect the detected INR by less than 20% of the result.

It's possible that with either meter - CoaguChek XS or Coag-Sense, a person should be able to have the incision and sample ready to go at or near second 0, incising the finger right as soon as the warming timer hits 0. (I may be wrong, but the Coag-Sense DOES have a countdown timer).

With the CoaguChek XS, it should be easy to test at second 0 if you put your finger near the strip just before incising it. I can't see it taking fifteen seconds to incise the finger, then touch the drop to the strip.

This question shouldn't be too hard to answer - just use two strips and two fingers - waiting to place the drop for one of the tests.

The clotting mechanism may not be linear - clotting may accelerate more, the longer blood has been mixed with the reagent - so the first few (15, perhaps) seconds may not be involved in much of the clotting -- it's that last seconds when clotting activity accelerates.

 

[user 16827]

So to update this thread iv'e had my new machine for a little over a year which i
use weekly

last week i had a NHS Lab venous blood draw followed within minutes with a finger stick
test on my Coaguchek XS to check the results for my own curious mind

Lab draw 2.6
Coaguchek XS 2.6


I'm happy with the comparison

 

[Protimenow]

It's good to be curious about meter vs lab comparisons. At one time - until a few years ago - I was inclined to trust the labs more than I do the meters. In fact, when I had a Hemosense and called tech support, they told me, bluntly, to 'trust the labs.'

Now, I don't feel that way. I've gotten some incredibly wrong results from labs - over and over. Leadville, I'm glad that you found a lab that appears to be doing it right.

I've come to the conclusion that the meter manufacturers - in the United States, this means Roche and Coagusense, and outside the United States also means Siemens, Roche, and probably a few others -- have a LOT MORE TO LOSE if their meters or strips give wrong results or, even worse, end up harming patients because of inappropriate response to erroneous results. They can be forced to recall strips or, in the case of HemoSense, completely remove the meter from the market. This could cost them millions of dollars.

Compare the cost to that of a lab that gives wrong results. The doctor sends the blood to another lab for confirmation. The doctor may use a meter to see if the lab result is within the margin of error. The lab keeps running tests, and may continue to deliver WRONG values. But the lab stays open. It doesn't discontinue its prothrombin/INR testing.

My point is this -- the meter and strip makers have a much stronger interest in having every test accurate. They put forth a lot of effort to assure that the tests are accurate.

If I could, I may do a monthly blood draw, out of curiosity, but would trust the meter before trusting the lab (or would have more than one lab run the test, just out of curiosity).

 

[pellicle]

So to update this thread iv'e had my new machine for a little over a year which i
use weekly
...
Lab draw 2.6
Coaguchek XS 2.6

its interesting, I (similarly to you) got variances like 0.2 ~ 0.5 or so when I first started but by the end of a year was getting close to or parity. Being who I am I like to hone my procedure to be very repeatable in as many ways as possible (probably experince in doing lab prac doing my biochem daze). I like to lance and have the blood on the strip within 10 seconds of the "ready alarm" going off (usually 5), and I like to have my rubber band wrap done ONLY when the alarm has gone off to minimise any potential effect (which I don't believe exists, but hey, be repeatable).

I believe that it is this repeatable and consistent approach in concert with minimising the times which has led to the agreement of lab and me. Further (knowing clinicians) I think its the labs failure of accurate and repeatable procedures (such as time between draw & test , storage in said interval, did they centrifuge and when ...) that may indeed explain the occasional weird lab result (they are human too and I developed this view in discussion with a senior pathologist from a major Australian Hospital).

Just because people work in a field doesn't mean they behave as a professional. Case in point is how much variance there was between clinicians who changed my wound dressing ... some were so effing miserable at cutting the dressing my mates 5 year old did better a job in cutting paper in kindy. I quickly learned that if I didn't want to suffer repeated "Chest Brazillian Waxes" when they were changing my VAC dressings (because they leaked and had to be redone) that I'd contact the supply company with a message of "don't send that person again" (with details on why). (after 4 months of this you get low on tolerance)

 

[user 16827]

Another update, I have had the new Coaguchek for just short of 18 months and over the last few months i
started to get the error 8 code again like the previous machine.

a reboot always sorts it out but on it's first attempt i always get the error code.

This morning i tested at 5.0 which caught me by surprise as last week i was 3.1

with the recent error code issue i was unsure if it was a correct result
test strip #2 was 5.0 also


I went to my clinic at 3pm and their machine tested at 5.1

They have provided me with a new machine which is a great service.

It shows ( to me ) that weekly testing can flag a result you may not be expecting,
i was certainly surprised.

 

[Protimenow]

I'm glad to learn that your provider replaced a possibly defective meter. Did they also replace the strips that were wasted?

Perhaps the medical system in England provides the strips, and was just able to replace the wasted strips.

I'm still using the Coag-Sense meter. I've had a few error messages - but very rarely have issues with strips. Most of the error messages have to do with inserting the strip too quickly (or too slowly) for the meter to read it. On my original meter, I was sometimes told to replace the batteries.

Unless I failed to put enough blood on the strip, or somehow got air bubbles into the blood (very hard to do with the new transfer tubes), the tests ran properly. If I got an error when I inserted the strip, I just removed it and reinserted it. The Coag-Sense strips aren't as time sensitive as CoaguChek - they're usable for a long time (some say hours) after removing from their individual foil packet.

When I used a CoaguChek XS, I wasted some strips - meter errors, not enough blood, operator error -- I had a meter fail on me, giving errors that couldn't be avoided just by restarting the meter.

I don't think that Coag-Sense is even available in the UK.

As I've said too many times before, here in the United States, the CoaguChek is my second choice of meters.