Significant Difference between Lab and InRatio2 Meter

[MarcoPolo]

I just got my InRatio2 Meter from Alere yesterday. My prior lab INR result the night before last was 2.5. The trainer tested me three times on the InRatio2 meter with results of 3.4, 3.7 and 3.8. We got those same three results on both the meter assigned to me and also the meter of the trainer.

Given the large variation between the lab and InRatio2 meter, I went to the lab last night and did a blood draw using the blood for both a lab test and putting drops on the InRatio2 meter. The lab result was 2.6 but the InRatio2 meter was 3.7.

I've spoken with Alere and they are asking me to go to the lab today and do another compare using venous blood for the lab test and finger prick for the InRatio2.

But is this level of variance normal? This seems so weird to me.

 

[dick0236]

I've spoken with Alere and they are asking me to go to the lab today and do another compare using venous blood for the lab test and finger prick for the InRatio2.

But is this level of variance normal? This seems so weird to me.

I also think this is troubling. Post the results of "todays" test. It seems strange that two meters would vary that much from a lab test......maybe the lab has a problem.

 

[lance]

XS is considered to be accurate if the lab test is within .8.
Maybe the manufacturer of yours has a known variance as well.
Here in Ontario monitors are recommended by hospitals performing heart surgery, require a doctor's prescription and require teaching in a hospital.
It doesn't seem the same stateside.

 

[Stopper]

I turned my meter back in because of the wide variance. It is convenient for me to go to the coag clinic weekly, so that's what I am doing.

 

[Protimenow]

I have reported similar wide variances between lab and InRatio (and InRatio 2) meters. When I called Alere to ask about the variance, they told me to 'trust the lab.'

In 2012, I had a stroke (the doctors called it a stroke, I prefer to call it a TIA) partially because I relied on the accuracy of the InRatio. The InRatio gave me a 2.6 -- the hospital pegged me at 1.7.

I did extensive testing of the InRatio, InRatio 2, CoaguChek XS, Coag-Sense, ProTime 3, and at the lab, and determined that, for my safety, the Coag-Sense is the safest (because it may actually slightly report LOWER INR than the lab). The XS is usually at or slightly above the lab values. I no longer trust the InRatio, and certainly would NOT bet my life on it.

Self-Monitoring is great -- especially if you do it weekly. Not all clinics agree with weekly testing. However, if the clinic is convenient and will do weekly tests, you may not need a meter. Based on your experience, you did the right thing returning that meter to Alere.

 

[MarcoPolo]

As a follow-up, when I did the home test within an hour of the lab test (using finger prick for the home test and venous blood for the lab test), I got 2.8 on one strip and 3.2 on another strip (two different lot numbers). The lab reported 2.6.

Based on this, Alere is sending me a new meter since there should not be that much variance between two strips done minutes apart. We'll see what the replacement meter reports.

 

[gerrychuck]

While others have reported InRatio 2's giving numbers varying greatly from lab tests, as you have, my cross-checking of mine with my local lab has been within .1 every time I have checked (equally over and under the lab results, to boot). Just another data point.

 

[UncleSteve]

I was just about to do my own post when I saw this thread. BTW I'm in the UK

I purchased my CoaguChek-XS last November from Roche, so I would have thought it would be 'spot on' (aka accurate).

A few mornings a go I had a blood sample taken by hypodermic syringe to take to the INR clinic, the dregs from the needle as the needle was taken out of my arm was used as a sample for my home INR test which was 3.1. However the clinic test was 3.8 which is unacceptably out (all the medical people I speak to want it to be within 0.3) for a new unit. So how do others get their CoaguChek XS re-calibrated. I have contacted the vendor, but they've not responded yet (from experience they quite often don't reply).

Why the Hypodermic method? Well I always have issues at the clinic trying to get a finger prick sample, so didn't want to faff around finger pricking (I have tried dunking my hand in hot water at the clinic, but their tap water is barely luke warm...).

 

[lance]

There is a known, acceptable variance with XS of .8 between lab and monitor. Your test is within that range. Check in the user manual this variance should be noted. I don't know why it would be different in the UK.
So were it me I would have performed a second finger-stick test.
As far as I know the .8 variance has held since 2006 without change and I've never heard of recalibrating an XS.
It sounds to me the medical personnel you are dealing with need to know their equipment needs calibration and XS either accurately performs a test or it doesn't test at all.
Here in Ontario the needles used for INR tests contain an anti-coagulant powder.

 

[Bina]

Since I don't own the INRatio model I can't comment on it, but I am quite sure that you should avoid using vein blood samples on the test strips.

With my Coaguchek XS (using finger tip) results compared with my hospital blood Lab (using venous blood), the results are
either exactly the same or within .2 of each other. ALWAYS.
I wouldn't accept the rather large variations that you are seeing in your testing.

 

[Protimenow]

There are reasons why the meter manufacturers want you to use capillary blood from a finger-stick -- and within fifteen seconds of making the incision. There are factors in the skin that promote clotting, and these influence the test results. With the exception of the ProTime meters, none of the meters are designed to test venous blood. You shouldn't expect that the lab results will match those from the meter.

(BTW: If I recall correctly, the acceptable error for the XS, and maybe for the other meters, is 30%. In my testing, I've found that the InRatio was almost always higher than the lab -- sometimes alarmingly so.)

 

[Marty]

There are reasons why the meter manufacturers want you to use capillary blood from a finger-stick -- and within fifteen seconds of making the incision. There are factors in the skin that promote clotting, and these influence the test results. With the exception of the ProTime meters, none of the meters are designed to test venous blood. You shouldn't expect that the lab results will match those from the meter.

(BTW: If I recall correctly, the acceptable error for the XS, and maybe for the other meters, is 30%. In my testing, I've found that the InRatio was almost always higher than the lab -- sometimes alarmingly so.)

This interesting. My internist has me check my seven year old INRatio1 once a year against a venous blood draw done by a good lab. One month ago I had this done. Blood drawn in the doctors office, Result INR 3.1. I drove home and within about 30' tested with the INRatio and got 3.0! We never test in his office by putting venous blood on the strip.

 

[MarcoPolo]

I continue to have wide variance between the lab and the Inratio2. I've now been through two machines and three different lots of strips. For the last three weeks, I've had the following results:

3/1 - Lab 2.8, InRatio 4
3/8 - Lab 2.3, InRatio 3.1
3/15 - Lab 1.9, InRatio 2.3

Alere is telling me that maybe I'm just not a suitable candidate for home testing, however, they also distribute the Coagucheck XS. Anyone switch between InRatio and the Roche device? I'd be interested in how the results compare between the two devices.

 

[dick0236]

You might stick your wife, or a friend. You should get an INR of about 1.0. If you do, the problem probably is with the lab. If your wife or friend test is not close to 1.0, then the problem probably is with your meter(s) or method.

About a year ago, I tested my meter(INRatio2), inr 4.0.... against my docs meter(coaguchekXS), inr 4.5.....and lab draw, inr 4.7. Your guess is as good as mine as to which test was the most accurate....although it did seem to prove that my INR was a little high. Ordinarily I check my INRatio2 against my docs CoaguchekXS once per month (he requires that I come in monthly even tho I home test weekly). I home test before I go in for my monthly doctors office test and we usually are within +/-.2. I almost never get lab draws anymore.

 

[Protimenow]

One of the basic problems might be that it is hard - even for labs - to be sure that their results are accurate. There are many factors at play -- if the blood is drawn and held until it's picked up (at a doctor's office or lab's blood collection center), is it handled properly? Does it sit in a hot car while a driver goes from doctor to doctor to doctor to get the blood? Is the reagent at the lab accurate? Are the proper testing procedures followed? Once or twice, I had two different samples (one at a hospital lab, the other at a clinic) within a few hours of each other. The values were considerably different. Personally, I trust the hospital's lab over a clinic's lab.

The idea of comparing an InRatio's results to those of a CosguChek XS may make you feel a bit safer -- but if they both report higher than lab values, this comparison could just be confirming that they both make similar errors. It's kind of like comparing two clocks that are equally slow (or equally fast) -- although the time on each could be wrong, because they're both close, it's easy to think that BOTH are accurate.

I don't know that I would derive a lot of comfort in knowing that an InRatio's results are close to a CoaguChek XS results. I'm not sure how comfortable I would be if the meter results were close to those from some labs, either. (There's another meter, not available to mere patients, the Hemochron, that is apparently used in Operating Rooms (and in my Anticoagulation Clinic) and it's supposed to be a gold standard for INR teting. I may take comfort if my Coag-Sense or CoaguChek XS results are close to those for the Hemochron). The major thing to try to do, I guess, no matter which testing method you use is to try to stay in the middle of your range -- personally, I would avoid going too close to the bottom of the range.

Dick's suggestion to test the blood of an unanticoagulated person (wife, perhaps?) and see if you get something close to 1.0 is a good one -- but it doesn't tell you whether or not your meter is accurate at higher values -- only that it does a good normal value. Some meters report values that have errors that increase as the actual INR increases -- an actual 3.0 may show up closer to 4.0 on some meters. Again - staying in the middle of range is probably the best strategy, no matter which way you test.

 

[bocco]

So I did a test today. I had a blood draw at about 8:30am. I then tested with my Inratio2 meter about 1.5 hours later at home. The self test was 2.8 the lab test was 2.5. I think I'm comfortable with these numbers.

 

[pellicle]

The idea of comparing an InRatio's results to those of a CosguChek XS may make you feel a bit safer -- but if they both report higher than lab values, this comparison could just be confirming that they both make similar errors.

of course this is where it 'could be' design. If I was designing a meter I'd get it to read lower than you were by a small margin. Considering how many people here write that they will attempt to sit on INR=2 because that's the lower end of the range. If you were 1.8 and the meter read 2.1 it would be cause for more concern than if you were 4 and it showed 3.5.

Then there is the issue of "is it accurate enough" ... I have a set of plastic vernier calipers here which I use to measure things diameters some times. Sure, not any where near as accurate as my G-clamp vernier, but then I don't use the plastic one to measure the shims in my Ducati's DESMO valve train at service, so does it matter?

If the variance in readings makes no difference to your dosing strategy then its of no consequence if its out by a margin.

 

[Protimenow]

Agreed. I would be much more comfortable with a meter that reported slightly lower INR at the bottom of the range than I have been with one that reported slightly high (as you stated). Ii was actually stung by the latter situation -- a 2.6 on a meter was a 1.7 (and a minor stroke) in the hospital lab). I prefer to have a meter that tells me 2.0 when my INR is actually at or slightly above 2.0 -- even if it tells me that my INR is 3.2 when it may actually be 3.6 or so.

With some in the medical establishment thinking that the NEW range for mechanical valves should be 2.0 - 3.0, I am very concerned for the home testers who believe their meters (as I did a couple years ago) and feel safe with an INR that is actually DANGEROUSLY LOW.

For most of us, probably the safest route is to shoot for a spot in the middle of the range, whichever meter we use.

 

[MarcoPolo]

I've now tested on both the Coaguchek XS and the InRatio2 for about a month and the results are either spot on or .1 apart with the InRatio2 reporting a lower result when they're not the same. Both are consistently between 12-26% higher than the lab during the same month. The manuals say that they are allowed a 30% variance from the lab results.

So now that I know that both report equivalent results, I have to return one of the machines. I'm thinking of returning the InRatio2. I read a study that seems to show that the retest rate of the Coagchek was significantly less than the InRatio resulting in lower costs of supplies. But while the study was labeled "an independent study", it does seem to have been paid for by Roche.

Any thoughts on which one you'd return?

 

[pellicle]

Any thoughts on which one you'd return?

I like my coaguchek XS, but that's me. I'd ask which you prefer?

I'd not pay much attention to the retest rates as that will be user dependent anyway. With respect to getting a sufficient sample try this method:

[ link ]


and follow the points I make in this post.

Which has the cheaper (to you) supplies?
I get strips for my coaguchek XS for about $138 for 24 strips