Just returned from the surgery after having my INR checked and it was 2.9 just re-tested at home on my coagu chek XS system and its 3.1 last time it was the same I get readings which are a 2 difference so which one is correct my system is 5 months old and the test strips have a long date , my target is between 2-3 the nurse said to come back in 12 weeks surely that's a long time to wait for another test

Also at the surgery I noticed the nurse did not use gloves there was blood on the strip which she touched after removing my test strip, I hope she changes the lancets with each check !!!!

34 Replies

  • Hi there,

    I use that system (Coaguchek XS) and go to my very supportive GP's INR Clinic every 10 tests and get my machine recalibrated against theirs. Our respective machines always give the same readings.

    I am assuming that your surgery check uses the same system. If however your surgery uses the venous draw INR testing technique it is unlikely that the results will ever be the same as the bloods go through quite different tests.

    In my 6 year experience with this device I frankly feel a 0.2 difference is nothing to worry about. So long as both devices (yours and the surgery) show the QC tick when you've dropped the blood on the test strip that's all you need to be concerned about. If it fails to give the QC tick your device should show an 'ERROR' message which you can check out with the User Guide.

    Why do you go to your surgery for an INR test if (assumingly) you are both using the same testing technique ( but with different devices).

    I take my reading at home on my device. Phone it to my GP's INR Nurse who, about 4 hours later phones me back with the next test date and the next dose, which she then confirms in hardcopy by mail. Simples. Then every 10 tests I go to the surgery and we do the next nominated test together on their device and on mine and compare the results. As I said the readings are always the same.

    I have never ever gone 12 weeks (84 days), but have gone 70 days for a long time. I get my test strips on prescription and so at about 35 days I'll do an additional test, just for peace of mind. My range is 2 to 3 and my target INR is 2.5. I rarely hit 2.5 but almost always fall in the range 2 to 3 specifically around 2.3 to 2.7.

    I don't like your practices health cleanliness methods. I'd be wearing gloves and replacing the lancets always as a standard practice - yeah, I share your concern on that point.

    Hope that helps.


  • Hello,many thanks for your reply when I received my coagu chek XS system I asked at the surgery, as its the same test device if I could have the testing strips on prescription and was told, no , they do not issue them in my area

    It would make life so much easier if the testing strips were available on prescription and of course I would save a fortune , your area sounds so much better organised.

  • When I was switched onto warfarin from Apixaban I had to attend the hospital about 7 miles away so that I could see the Anticoagulation nurse rather than our local memorial hospital (where I now go) which just has phlebotomists. At that consultation the nurse explained that they do not use the test strips as the cost is over 6 times higher than the venus draw method. My suspicion is that it is not 100% a true comparison because the labour costs have not been factored in.

    When deciding I think a trust's key consideration is volume. It is a small town where I am and they typically do 120 or so every week. That probably means about 900 people since some go weekly and some thirteen weekly. The next hospital by distance runs 4 Warfarin clinics per week with four phlebotomists and then there further two hospitals are bigger again, one being a full blown hospital with A&E, etc. On that basis the trust is probably doing 3,000 warfarin tests per week. In addition there are all the other blood tests that are done at separate times every days of the week. With that volume they are getting efficient use of the lab test facilities for the venus draw ones and therefore have a good (cheap) price.

  • Hello again,

    When I was diagnosed with AF and put on Warfarin my local GP's surgery had all nurses trained and equipped with Coaguchek Devices, which is where I got my introduction. At the time I was a bus driver on shift work and so getting to all these INR tests was very, very difficult. I asked the surgery about buying my own and they not only encouraged me, but offered me 'support/training' in using the machine but prescribed the test strips to. At the time I lived in Surrey. Then I retired and moved to Cornwall. There began all my troubles. The nearest practice only did the venous draw from a vein in my arm. I kept banging on about using my Coaguchek device and they said no. I made a formal complaint to my local CCG who promised to look into it - well that was a waste of time. In the end I did a phone ring around of local (to where I lived) surgeries and found one who did both venous draw and Coaguchek. I was taken on their books - quit the old practice and have never looked back.

    If you had the energy and could afford it you could always buy a pack of your own test strips direct from Roche - do your own tests which would be recorded on your device, then take your device to your surgery and present them with the reading. It would be really interesting to see their reaction and see what they would do. Again, if you had the energy and the time I'd write to the practice and make a formal complaint that their attitude is counter to NICE Guidelines and that unless they prescribed the test strips you would make another formal complaint to your local CCG.

    From what I've seen on this and similar websites your experiences and those of PeterWh are fairly common and reduces the whole thing to a post code lottery.

    Good luck.


  • Ouch, the troubles you had. Last summer I asked a few doctors in UK, what would happen if they had a new patient who was on Warfarin, and was self testing and self dosing. Could they insist on taking control? Answer: they could try, and you would have to quietly and diplomatically stand your ground. But, ultimately they could write you down as someone who insisted, and they would deny responsibility for error etc. The trouble then is they can start playing power games. If you can afford the strips and like it, do it yourself. The problem is prescriptions for Warfarin.

    Are there any legal experts on this forum? What legal right does an informed capable patient to refuse the advice of a doctor?

  • I would have thought that a difference of 0.5 is too high. I would have thought 0.2 max or possibly at a stretch 0.3.

  • I think this topic needs another thread and I do not have time now. There are several strands to consider: reasoning, on the ground experience, and the research journals. From what I remember, variation is more than you expect.

  • Hi there,

    Just on the topic of your last paragraph - and moving into the legal framework one should consider the following NICE documents;

    1 NICE guidance CMG49

    2 NICE guidance CG 180 and

    3 NICE guidance DG14

    I don't know if you are across them but they make interesting reading, in particular CG180 and the reference to the NHS Constitution for England.

    Prior to finding a local surgery who would provide me with the service I want I was getting to the point of making such a challenge and involving my MP. Regardless of what the doctors told you they would I reckon be batting on very dodgy ground. Doctors nowadays are like what in the commercial world we refer to as cartels !!

    And of course the problem we have now is that this current government in its previous life changed the financing of the NHS by pushing financial budgets down to local CCG's and local Surgeries so at GP level the Doctor Cartel is obviously going to ignore what NICE say and refuse certain medical activities on the grounds of money, and they will do it a number of ways, none the least is to say for example, the patient is not capable of taking his or her INR.

    I think sooner or later this will come to a head.


  • I actually believe that cost should be part of the equation. However also a key aspect is local facilities and local practicalities.

    For me yes it would be nice to be able to self test on a coaguchek provided by the NHS and strips provided by the NHS. I did ask but was told no even to strips for my own coaguchek. However put into perspective the local CCG (aka Trust) runs dedicated warfain clinics in at least 4 hospitals. In my case the local memorial hospital is less than 2 miles away and the are getting on for 30,000 people within 3 miles of it. No parking charges, walk in anytime from 8.00, if have to wait more than 5 mins very unusual. For those who cannot make the Wednesday INR blood clinic there are ones other days and also GP's surgeries will do if real problem.

  • OK whilst I will not comment on John's post since he has been doing this for years I will say that INR testing is far from an exact science. An error such as your is quite normal I think although it may be worth you checking your machine against the GPs when next you go. Another thing to mention is hand washing. Do you always wash your hands just before the test? I always do and have found that should I not dry them properly I get a lower reading than expected.

    The phlebotomist will always use a new lancet. They are a once only item.

    12 weeks is not unusual if your INR is stable. I was at that period for a year or so until I had to have extra tests as a result of antibiotics.

    My own very personal view is that most people worry far too much about INR testing. Provided that you are in range my only concern with the Coaguchek system is that it does not recognise rising or falling trends. Hence you can be say 2.3 and it will continue to advise the same dose which may allow you to fall our of,range. I watch out for this and discuss with my phlebotomist to ensure that I don't.

    The lecture we had some years ago at HRC from a specialist in INR testing suggested to us that 2 to 3 was perhaps not the best range to aim for due to the inaccuracies of the system. INR testing in a lab is particularly prone to outside influences. The comment was that 2.5 to 3.5 was a better aiming point to ensure total cover but that up to INR 5 was not dangerous. Current guidelines remain 2 to 3 however.

    Hope this helps.

  • Thankyou Bob you have eased my mind just going to have a spinach, broccoli and apple smoothie now

  • Bob I am assuming that you are talking about teh professional Coaguchek system when you talk about rising and falling to trends because the XS for home does not have any features for predicting.

    The CCG (aka Trust) where I am uses Venus draw but the programme does not recognise rising or falling trends. From the weekly tests I keep track of trends and then if it is likely to go out of my range of 2.5 to 3.5 then I phone them up and agree the dose. On at least a couple of occasions I did alter the dose myself without discussing because of being unable to get hold of them as it was long weekend. Got it spot on!!! They didn't seem to mind.

  • Peter, The surgery uses the same machine which as you say has no dosing facility. They then feed the result into their computer system which predicts the required dose but as I said it does not see trends so one needs to be proactive and watch for oneself.

    I would never dream of suggesting that another member alter their own dose but what I do in the privacy of my own home is my business. I also find an extra glass of red is helpful for fine tuning.

  • OK. I was taking your words absolutely literally because I knew there was a medical use coaguchek (larger and used in local hospitals and at Barts) and I thought that had the facilities. The program your local surgery uses is probably the same one that the local trust uses.

  • "Does not see trends..." That is terrible. How then can it be trusted? For instance, I have sometimes been out of range twice in a row, I have made no dosage change, and the third and subsequent results were within range. The range of variation which is natural in some people is quite wide. Premature dosage change can make things worse. It can create faster swinging and more extreme results.

    Interesting, that even the simplified scheme below recommends two out of range results before changing the dose. I quote a reputable journal and give a free link below.

    "The algorithm recommends no dose change when the INR is in the therapeutic range, a 10% adjustment in the weekly dose of warfarin when two consecutive INR results are out of range by no more than 0.5 units below or 1.0 unit above the therapeutic INR range, and a 10%–20% adjustment in the weekly dose of warfarin when the deviation from the therapeutic INR range is more extreme.

  • Hi,

    This algorithm is the guideline, if you like, that I use when on the rare occasions I feel it necessary to self dose.


  • Just a few minutes ago I decided to break this guideline. One result below 2.5 so I am making a small increase tonight, test again in a week. Why?

    1. Because two weeks ago I made a small increase and it has still come down,

    2. I am at the tail end of getting Amiodarone out of my system, and I could predict from the first t-half, that I needed to increase my Warfarin soon. I was expecting the INR to go down, therefore it is unlikely to be the normal random result.

    3. I always act quicker for low INR than for high INR.

    4. I have done no harm by not waiting, and using a slight dose increase. It may well not be enough. I shall see next week.

    I do not know if the computer program is capable of including these factors along with others and prioritising them.

  • I was told that to do an accurate cross check of a home device someone had to take their machine in and a drop of blood from the same prick put on each of the slides and then one inserted into each machine at the same time.

    Round here they won't use coagucheks / prescribe test strips because of a good local Anticoagulation unit covering four hospitals. However I bought my own coaguchek because my INR was shooting all over the place (swings of 2.5 week on week) and for teh period after my ablation I wanted peace of mind that I was anticoagulated properly. At least 3 times I have cross checked the Venus draw INR result against the Coaguchek and on all three times it was a +0.1 difference.

  • Just remember, it is significant change which matters, not just the figures. By using one machine all the time you are achieving greater consistency -- researchers call it 'reliability'. I would trust the machine you have, and double check if you are suspicious. Lab technicians also make mistakes so venous testing is NOT the gold standard.

  • You are absolutely right re consistency but all machines (not just coagucheks) need calibrating or cross checking from time to time.

    I actually rarely use mine because I am on weekly testing because of being on waiting list for second ablation. I bought mine for the run up to and particularily the period after my ablation because my INR was swinging all over the place at that time and I did not want it to drop to low after ablation (which it dis to 1.7 I think so it was well worthwhile. I use it when I can't make local hospital (eg when I was on holiday).

  • Agreed. All machines need cross checking from time to time. I must not forget that. Interestingly, the FAQ on the coaguchek site seems to say that it has its own quality control checks therefore cross checking is not needed. Hmm. Well, common sense must rule. A once in a while comparison (once per 1-2 years) with venous blood cannot harm matters provided you accept a rough correlation, say, not more than 0.5 difference. I seem to remember seeing research on this.

  • I think you will find that the reference to quality control checks refers to the devices capability to ensure that when the test strip is located into the device that the test strip is not in itself defective. If it is defective, an ERROR message will appear on the display. It also ensures that the test strip falls within the use by date range - all aimed at providing the most reliable INR test result.


  • Hi Peter,

    By agreement with my surgery we cross check our machines once every 10 tests, so far both have produced the same result. Basically, one finger prick produces the blood which is then dripped/placed/located - whatever you like to say, on both test strips on both devices.


  • That's the correct way!!!

  • Also 10 is probably very cautious!!!

  • I do my own checking and have to phone result to the hospital clinic,leaving details on answer phone..They only call back if a change in dose is neede,and confirm by post which also gives date for next test. They check the meter as the previous comment said. I remain well in range, usually between 2.4 and 2.7 . It's well worth pushing for home testing, it allows more freedom

  • Reading these remarks about Warfarin,it sounds so complicated,why do people not change to the newer drugs e.g. Apixaban etc. ? Same results,less worry!

  • Some people have to stay on warfarin & don't have the choice to change. I had my mitral valve replaced sometime ago & was told I will have to stay on warfarin for the rest of my life. This may change in the future but the situation here in NZ is that those with mechanical valves have to stay on warfarin for now.

  • Hi,

    I have no problem with warfarin - so - if it ain't broke, don't fix it. Apart from that I don't believe these newer drugs have got much of a track record so far and not all of them have any antidote as warfarin does. In other words I don't trust them. I know that in Australia the Australian Government Theraputic Drug Administration has issued a range of Health Warning Advisories about Dabigitran. So, no way.


  • Hi,I have only been on Apixaban for 9months! The main barrier to prescribing this in UK is money!

    Yes Warfarin is a much older and cheaper drug that's the attraction in UK!

    Modern safe drugs are now used in Europe!

    The Antidote argument is a "red herring" they're relatively short acting( Apixaban is taken every 12hrs)

    But it is personal choice!

  • I bought my brand new coagu chek machine from Roche 5 months ago,used around 10 times cost £299 surley the results should be accurate

  • Mine has been very accurate. Recently though i had a wildly " out" "reading . 5.7 and then 4.8 and 5.1 on a redo. At the doctors later that morning it was 3.7. I phoned Roche and they replaced it with no questions asked. It arrived within 48 hours. They rang me to say they had tested my machine and they explained how that was done. They could find nothing wrong but the machine has a "history" so they could see i was telling the truth. I have put it down to the fact that i had taken my once weekly alendronic acid tablet that morning. Perhaps that had done something to my I.N.R. Anyway i was so impressed with the company for their quick response and no questions asked policy. X

  • Yes it almost certainly will be accurate both now and a long time to come. However all medical test equipment and also all test equipment in industrial applications have to be tested at periodic intervals ranging typically from three months to three years depending on what it is and its usage. Some equipment can lose calibration by being dropped but this is much less of an issue now than say even 10 years ago due to use of electronic components.

  • I coagu chek at home, and every 6 months go to clinic for a venous comparison test with my anticoagulant nurse specialist. My machine always slightly differs from the venous result but has to stay within a certain accepted range.

    I have been following this protocol for years and I am 100% confident of the nurse that looks after things and sets my dosage. Please don't worry or give up on self testing