Unexpected and Question

[Granbonny]

To the Resident Nut

To the Resident Nut

Stick it..Poke it..Jab it..Have fun with it..What are you talking about??? I thought I had you improving ..Careful I may have you in lock up again Bonnie (Resident's Nut's Therapist)

 

[EVELYN]

I just got off the phone with Lakeesha from tech support from International Technidyne Corporation in New Jersey, makers of the Protime machine;(732 548 5700 x 274) basically because I was pretty sure of what she told me the last time I spoke with her, but wanted to verify the information I was told a few months ago. It absolutely is NOT my intention to give misleading information to anyone on this list.

Here is what she told me: The Protime machine has an ISI of 1.0....the Coagucheck has an ISI of "around 2." If you test on both a Protime and a Coagucheck with the same blood draw, the difference can be UP TO A .6666 RANGE between the two machines, Protime being lower.....ie. if Protime gives an inr of 2, Coagucheck will usually give an inr of up to 2.7.

She also said that within Protime, the cuvettes also can make a difference. The 5-channel cuvettes can test lower than the 3 channel cuvettes.

I do not think I heard it wrong a second time.

Evelyn

 

[KIRSONRON]

Again I think you are being given incorrect information. I have the ProTime Operator's Manual in front of me now. This booklet is written by ITC and was published in July 2001. It should have come with your unit - it not, you can obtain an Adobe formatted version from ITC's website. On page 35 in the "For Professional" section, the relationship between INR, ISI and Prothombin time are clearly defined. Let me quote you some of their writings "The INR system was introduced by The World Health Oraganization to standardize PT (prothombin time) reporting such that patients could be unifrom accross different laboratories". In the past, PT was used to report clotting, a time value that varied with the ISI that the laboratory used. This was very confusing to doctors since each lab used a different strenght reagent - (different ISI). The INR eliminated this variation by converting all prothombin times to an International Normalized Ratio (INR) based upon a calculation that took into account the ISI of the labs reagents. This formula is also shown on page 35 What I think ITC was trying to say is that if you look on page 36, you will see a table showingthe relationship between PT seconds vs. ISI - for various INRs. Choose any INR in the right hand column - for example 2.5. The PT for an ISI of 1.0 is 32.6 seconds while the PT for that same INR using an ISI of 2.0 is 19.5 seconds or approximately .666. Using the programming plug to change the ISI of the ProTime forces the machine to report an adjusted prothombin time - again on page 35 this is quoted ..."Since results reported i PT seconds depend on the sensitivity (ISI) of the reagent employed, the physician has the option of changing the ISI value in ProTime so that the ProTime results reported in PT seconds closely match the results reported by the hospital laboratory".

I guess what I'm again trying to say is that INR was supposed to eliminate these variations, allowing for a direct comparison between readings taken anyplace that reports them as an International Normalized Ratio (INR). If you correct INR for the difference in ISI, you will be putting yourself in a very dangerous position. It is the clotting time that is different, not the INR result. I suggest you call again and ask to speak to the technical supervisor and get this clarified to your satisfaction. Stop chasing results, trying to match them from lab to lab. Either trust the ProTime or Coagucheck, whichever you use or get rid of them and just go the the lab. Its not worth the stress sweating variations that are probably more attributable to lab technique, sample handling and diet/exercise variations.

Sorry if this is rather long. I just shudder to think that others may be adjusting their readings based upon your e-mails and then changing their Coumadin doses to try and get everything to match.

 

[Guest]

We can't dispute that Evelyn is giving the true information that Lakeesha gave her. However, I don't think that Lakeesha is giving correct information. When she says that the CoaguChek has an ISI of around 2 -- she is showing that she is not giving factual information. The ISI of CoaguChek is 2.0 and has been for the past 5+ years that I have been using it. Therefore, I would mistrust anything else that she said.

Would somebody call her and pin her down on what peer-reviewed medical journal this 0.666 factor was published in. Get the year, volume, page number and author. Otherwise you can just put this down to a sales person trying to fluff their own product while dissing a competetor. No more believable than a used car salesman saying that it was only driven to church on Sunday by a little old lady.

 

[QAS]

I do believe that Lekeesha was merely stating that from lab to lab, monitor to monitor, etc., a .666 difference is the allowable mean. She is not a salesperson, but a technical support assistant for ITC. Her number is listed in the previous posts, for those of you who would like further clarification. From what I've learned, an ISI of 1.0 is recommended by the American Heart Association (AHA), the College of American Pathologist (CAP), and the World Health Organization (WHO). The majority of the time, when a laboratory is performing a correlation study, one of the strongest selling points is the ISI 1.0. I cannot argue the accuracy of the CoaguChek, as we all know both monitors are found to be very acceptable monitoring tools, but I can share the benefits of the ProTime Monitor. Feel free to call any of us at QAS, and we will do our best to justify all of the benefits of our instrument.

Lance

 

[Guest]

I agree with Lance. There are hundreds of thousands of both instruments in use with good results.

This is exactly what I hoped someone from QAS would write. You cannot just add or subtract a factor that will apply to every one of these instruments.

 

[Hank]

What are we talking about?

What are we talking about?

Ok Folks - All things being equal - or not equal, what we are really concerned with is monitoring our INR's at home without having to go to a stupid lab every 2 weeks or every month or whatever.

I personally don't concern myself with any possible differences between the machines. You are never going to be able to keep your INR in a 0.666 range anyway.

For my valve (mechanical St. Jude in aortic position), the AHA recommends an INR of 2.5 to 3.5. I personally would rather have it 2.5 - 4.0. (better to bleed than clot theory).

I use my ProTime to monitor trends and drastic changes in my INR. I wouldn't be able to fine tune it to a .6 tolerance anyway. My diet and inconsistent life would make that impossible.

My point is this: The home monitoring machine should be used to establish a personal baseline (norm) and then used to identify trends and such.

I hope I am making some sense here. But probably not.

Anyway - Let the controversy continue so we can continue to learn from the debate

 

[Granbonny]

Thank you, Hank

Thank you, Hank

I was beginning to get swimmy headed from all the Tech. talk..I just worry more about getting my blood to flow..so I don't ruin a cuvette. I'm trying to live a normal life rather than worrying about my INR every hour, every day...I really think my Clinical nurse thinks I take it too often..every 2 weeks..but she is so sweet and always calls back and say..stay on same dosage and test again 3-4 weeks. Bonnie

 

[Ross]

I'm trying to live a normal life.

You can't do that if you talk to me! I ain't normal and you know it.

 

[Granbonny]

Bill's cartoon under Ref. source

Bill's cartoon under Ref. source

Posted by LA Cruiser reminds me of me and you.. We need a life Your Therapist

 

[EVELYN]

I said to myself that I would not deal with this issue on this list as I do not need to be flogged and burned at the stake again, but I have since donned my armor and my flame-retardant suit and will post exactly what I was told from Dr. Marcia L. Zucker, Director of Clinical Research at ITC, 800 631-5945, extension 213, [email protected].

Dr. Zucker contacted me, at Blanche's request, to clear up the problem she perceived I was having with the INR rates between different labs/coagucheck machines in comparison to the Protime. She said that they, "frequently see differences between labs and point of care systems." and with the Protime machine the "difference can be up to .6666, but that does not mean that everyone will always see a difference every time."

She also went on to say that the "plug has no effect on INR results, just converts the values of the ISI from 1 to 2."--which I knew.

She continued to say that Lakeesha was correct in what she told me and said that I was like a "breath of fresh air," in that I realized poc systems and labs can and do have differences and as long as you're within the variables it's ok.

I like our Protime and trust it completely. I'm also very satisfied with the explanations received from Lakeesha and Dr. Zucker. I know that there can, may, might, and probably will be a difference of up to .6666 in comparison tests, and I'm NOT going to worry about it any more, so knock yourselves out burning and flogging.

Evelyn

 

[Guest]

Evelyn,

You are a true scientist. You are to be commended on your quest for truth. This is a well-written explanation of the "problem" with various methods of testing.

Flogging and burning ... remember the Church condemned Galileo to eternal Hell for saying that the earth went around the sun.

This problem with testing has plagued warfarin since it was first brought on the market. Prior to the INR system coming into use about 1990 the testing system was much more crude and there was no way to know what the actual reading was even from day to day in the same lab.

I know one person who worked in a hospital lab about 20 years ago. Every morning a person went to the lab and had a protime done. That person's blood was the standard for the day. Then everyone else who had a protime that day had their warfarin adjusted to try to keep their protime between 1.5 and 2.5 times what this "control" protime was. What they did not realize was that some of the testing material was fairly insensitive. (Today we would say that it had a high ISI.) This resulted an 1.5 times control corresponding to an INR of approximately 8 !!! No wonder people bled and there were all sorts of horror stories about warfarin.

Again, you are to be commended on your quest for truth and clarification. As we all know there are very few absolutes in medicine. We are all on a continual quest for what works best. Thanks for your very valuable contribution to all of our knowledge.

 

[JimL]

Al, I thought Galileo got it right, "It [the earth] does move." ONE church, anyway, condemned him, along with a lot of other people.

Not to add confusion to an issue, but rather to confess my ignorance: Somewhere I heard that there are various kinds of tests, all called prothrombin, PT. Then for each test there is a conversion factor to turn the PT into an INR number. Theoretically, the INR should be the same for all kinds of tests, while the PT would theoretically be different for all kinds of tests. There, I think I've confessed enough ignorance that someone will surely correct me and educate me. Perhaps the answer is that even with all the theory, there still practically are differences in the INR readings.

 

[Guest]

I edited the earth-sun thing and I think I got it right. Maybe I will only have a short stay in Purgatory!!

You are correct that the INR is a mathematical realtionship between the Pro time, and the sensitivity of the material used to run the test (ISI). Because the formula uses the ISI as an exponent, it works best when the ISI is 1.0.

The INR is accurate to compare different results, but because some materials (CoaguChek is an example) have an ISI higher than 1.0, the INR beging to become less meaningful the higher it gets. It is very useful for comparing results near the desired ranges.

It is true that the Pro Time is more accurate because it has an ISI of 1.0. However, this is not rocket science - we are not calculating the amount of fuel we need to get to the moon and back. An ISI of 2.0 is perfectly acceptable for INRs up to about 5.
If the person's INR gets above 5.0, you need to make an adjustment whatever the ISI.

The way that I treat patients above 5.0 is to hold a dose or two of warfarin if they are not bleeding. If they are bleeding then steps need to be taken to control the bleeding. So, while it might be nice to know whether the INR was 5.1 or 5.2 from a scientific standpoint, for reality it doesn't matter to me.

To use a car analogy, the speed limit is 35 and you are pulled over for speeding. Is it going to make any difference whether you were doing 51 or 52????

 

[Zipper]

Hi Al,

I hear what you are saying and stayed out of this dicussion until now. Quite some time back, when I received my ProTime unit, I posted that I did a three way test with my Lab at the hospital I work at. The first thing my Lab tech checked is the ISI, and told me the compatability of calibrations.. Then we did a three way test. The venous draw was used to be analyzed by the Lab and drops from same used in the curvette. At the same time we did a finger stick....Now I forget the exact #'s...it's in the archives...but I do know they all were 2.something which was quite to the satisfaction of my Lab, my Cardio, and therefore myself. As it's been so controversial here lately, I hesitated to reiterate my findings.

This is why I personally am very confident with home testing altho I still visit my Lab every so often since my insurance denied payment, citing it to be a 'medical device' not of necessity to patient. BTW...to my understanding...this is the stand Medicare is taking also. I posted regarding that as well.

Thank You for clarifying this ISI issue!!!

Zipper

 

[Guest]

Just when we think that we have that nailed down, along comes a new gunslinger who wants to make a name by knocking off the top gun.

In the November 2002 issue of Pharmacotherapy, Shermock et al ([email protected]) of the Cleveland Clinic published an article titled, "Differences in warfarin dosing decisions based on international normalized ratio measurements with two point-of-care testing devices and a reference laboratory measurement.

Their finding was that the AvoSure device produced a reading that resulted in making the same decision as the reference lab reading regarding a warfarin dose 78% of the time. The ProTime device gave a reading that resulted in making the same warfarin dose decision as the reference lab reading only 66% of the time. This was mainly because the ProTime overestimated low INR values more often.

 

[Zipper]

An art for sure

An art for sure

Geez...on it goes....let's not forget that with venous draws the techniques of the lab techs can also produce varied results! It certainly is NOT an exact science..but nothing in medicine is! Thanks for the info, Al.

Zipper *~*

 

[KIRSONRON]

Could you please define "overestimated low INR readings"? Does that mean that Protime's INR readings were somewhat lower than a reference lab or that the INR readings came in on the high side?

 

[Guest]

I just quoted what the article said. I take it to mean that the ProTime gave a higher number than the reference lab when the INR was on the low side.

I didn't want to mix my opinion with the statements in the article but now that they are separated, I will give my opinion. Overestimating a low INR is a serious situation. You are much more likely to suffer serious consequences from a low INR than a high one. A low INR can lead to a damaged valve or a stroke. A high INR most often results in only a bloody nose, or possibly blood from the bowel or bladder. Serious bleeding is fairly rare.

 

[KIRSONRON]

I was asking because the Protime readings I get are somewhat lower than the quarterly lab readings taken during the same time period.