I have posted on here on a number of occasions my views on the two methods of INR testing. Venous Draw v Coaguchek home testing.
Firstly, to recap.When I lived in Surrey, my surgery was fully equipped with the Coaguchek XS testing devices which included the software installed on the practice computers for INR bloods analysis and for calculating new dose and next test date.
At the time I was diagnosed with AF and put on Warfarin I was working full time as a bus driver (working a variety of shifts) and so it became more and more difficult to get to the Surgery for my INR blood tests. I also travelled quite a bit to Australia and still do. I approached the surgery about acquiring the Coaguchek XS device and they agreed that it would be a big help and through the practice nurses - they would help me with training and support and also put me on their 'system' so that I could telephone in my test results. I used to telephone in my INR result from the Coaguchek device, tell them that I had not missed a dose and that there had been no variation to my medicines. They would then phone me back about 4 hours later with the INR result, the next test date and the next doseage to be followed up to the next test date. So simple.
In effect my visits to the practice for INR blood tests would cease unless I had a problem although they would like me to pop in twice a year to check the readings on my device with their device. I've never looked back, and of course, getting test strips on NHS prescription was never an issue.
Onto Cornwall .....I moved here in late July 2012.
Imagine my dismay to find that my local Cornish GP's practice only did the Venous Draw technique. Blood letting from the arm ! Sending the bloods away and waiting for 24 hours to get my INR result. I had not had this technique applied to me for INR tests and so was quite distrusting of it. Accordingly, I used my Coaguchek device to cross check the results of the Venous Draw. To cut a long story short - in the time that followed, my Coaguchek device showed some small variations in results but nothing untoward. I did however, in that time, have to challenge the doseages on two occasions and this caused my GP's practice to revise the doseage. Can't say why these errors crept in, I did get apologies though - although that wasn't the point. The point was my doseages were WRONG ! This did nothing to enhance my confidence in the Venous Draw technique. Meanwhile, I continued to use my Coaguchek device to cross check the Venous Draw and of course I used up my test strips. In November 2013 I returned to Australia for a holiday and was low on Test strips. Went and saw one of the partner GP's in my local Cornish practice and got a new pack of 24 test strips - without qualification !!
Fast forward now to a more recent Venous Draw - Test result showed 3.5. Coaguchek result showed 2.7 taken 20 minutes before the Venous Draw.Now, I am quite prepared to accept that the two techniques may not produce the same result but I was nonetheless unhappy about this variation, particularly as my new doseage was quite a dramatic change, i.e. I had to miss one day's Warfarin altogether and reduce three days doseage from 6mg to 5 mg so that the following 6 days were all at 5mg. I decided ( as I was now going to run out of Test Strips yet again ) that I'd go back to my GP and ask for a new (Aug 2014) prescription .... and I also did some research to support my request in the event that I was refused..... because I was quite determined to fight for the strips if I had to.
Now its this research bit that may be of interest to you Warfarin users, and I'll try and be brief and list the source documents below -
1) NICE (6/02/2014) published DRAFT GUIDELINES on self monitoring tests for people on long term anticoagulation - Ref: nice.org.uk/News/ Press-and-Media Provisional recommendations - support the use of the Coaguchek XS system for people with atrial fibrillation or heart valve disease who are on long term anticoagulation therapy. Significant benefit is enables patients to be monitored more regularly; improves health outcomes; doses can be adjusted more accurately. You could also go to cks.nice.org.uk/anticoagula... - a 60 odd page document on the matter of anticoagulation oral.
2) Google ...... ptinr.com/warfarin-you - then go to How often should I testmy INR and Testing methods for your INR you will find the comments about Venous Draw and Finger Stick testing - both point of care and home testing very interesting. Especially the bits on 'reagents'.
3) Reference : who.int/bloodproducts/ivd/t... will give more info on reagents ..... and finally,
4) anticoagulationeurope.org/a... self monitoring
So, at the end of the day - having done all this research I fronted up to discuss my INR results and request a new prescription of Test Strips only to have no argument at all and got a prescription for another 24 test strips just like that. We did have a discussion which amounted to my suitability to self test and that was it. Once the GP was totally satisfied that I was suitable self testing material it was all done and dusted.
Then it came to agreeing to a date for my next appointment - and I said I couldn't keep that appointment due to work committments - why don't you accept my Coaguchek Finger stick reading, I asked. I said I could phone it in on the said day and get the results the next. And to my total amazement - he agreed. So I did that and phoned in my latest reading which turned out to be 2.3 from my Coaguchek device. In effect - in 2 years this surgery in Cornwall has shifted its position on INR testing from the 'old' system of Venous Draw ONLY, to doing both Venous Draw and the 'Coaguchek' system - which also means supporting those patients on Coaguchek by prescribing on NHS the Testing Strips. Still not as advanced as my Surrey surgery but moving along in the right direction.
The one thing that is clear from my research is that the Venous draw technique is the least perfect of INR testing techniques - it is very susceptible to the quality of the commercially produced 'reagents' and to the skills of the laboratory technician. In fact, both patients and physicians are usually unaware of the sensitivity of the 'reagents' used in any given laboratory. The Coaguchek system uses only 'reagents' with the highest sensitivity available in their test strips and unlike laboratories, where this sensitivity can vary, products like Coaguchek test strips have the most consistent high quality 'reagents'. In my opinion - this means that something like Coaguchek is the more perfect, more accurate and more reliable system.
Those of you interested can refer to the source documents I’ve listed and read for yourselves.
Apologies for the length of this I'm not a jouirnalist so couldn't edit it and make it much shorter