Finger Prick & Vein draw trial

[WendyWoo50]

My anti Coag team think it would be a good idea to have a months trial whereby I have a finger prick then vein draw one after the other once a week to compare reading accuracy.

They have found in the past that there is often better control of APS patients using vein testing.

I’d be interested to hear from anyone who has undergone this trial. What were the results.

For those who only have vein testing - do you feel the INR is better controlled?

Thank you 💋

[HollyHeski Administrator]

It sounds a good idea, I'm not on warfarin but I know others that have tested both, especially those that self test at home.

Others will answer you soon x

[Wittycjt]

Certainly cant hurt- go for it! When i was on warfarin i did this and it was only off very minutely so i couldve continued but i like the lovenox better- can eat anything and just keep my weight the same. Two benefits: i dont gain unwanted weight and i no longer worry about too much Vit k- that made me quite anxious. And if I get it on ninety day supply- my insurance covers most of it. Just need to store it in appropriate temperature which is usually my house temp anyway

[leakeadea]

I recently saw Professor Cohen at UCLH (who was marvellous by the way) and she said regular vein testing is what they recommend for their APS patients because the finger prick machines are not accurate.

I don't know what machine your anticoag team is using but if it's similar to the Coagucheck then it won't be accurate. Coagucheck themselves will not guarantee the results if you have APS, in fact they send you out a red envelope with information inside, explaining the reasons why Coagucheck cannot guarantee the results for those with APS. Apparently the antibodies affect the results, also if you have anemia, this will also cause false finger prick results.

Professor Cohen doesn't want me to use my Coagucheck machine at all, she insists on vein testing with APS.

Hope this is helpful.

Claire 👍😁

[Youmi111]

I also have the finger prick machine at home. I did my INR in the morning then went right over to the hospital to have a vein blood draw and the machine was just of a .10 off. So mine is pretty accurate and I do mine at home. Also your blood draw will differ from morning to night so to ck the accuracy - pick at home then go right to the lab for vein draws. Hope this helps.

[Ray46]

The trial is not a problem (let the clinic decide whether they dose you off fingerprick or venous - they can always correct if venous comes through very different a day (max) later).

I had to do this where I am before they would accept me onto self-testing - when starting warfarin they only did one or maybe two comparisons, Coaguchek then used in clinic, but for self testing they wanted comparisons for two-three months (they _may_ do that for APS patients as standard now in clinic, as they are more clued up on APS than when I started).

What I would do is make sure you sort out what the parameters of the trial are, and what the pass/fail criteria are, in advance - they should be able to tell you and if they won't I'd be concerned that they are making it up as they go along, which isn't good.

There aren't any standards or guidelines for this (that I know of), and probably not a lot of agreement among doctors either. In my trial I was dual-tested every two weeks, but for three or four months. Testing should be at same time/place as far as possible (sit down, needle, vein sample, fingerprick right after they patch up your elbow, in my case). I'd question whether a month is long enough, only 4-5 tests, for me they wanted more like 10. Also, they wanted a range of values, as I understand it some people's results diverge more as INR increases, if you are 0.1 different at bottom of range but 0.6 different at top, that could be a problem.

Success criteria they used for me was I think:

(1) consistent difference vein-fingerprick (<0.3 variation in difference, I think)

(2) difference to be <1.0.

Note that failure on the criteria would also mean vein testing always in clinic, as well as no self testing.

In the event, I passed (and now self-test) - BUT I did have an episode before the trial period when fingerprick INR shot up to more than 1.5 above vein, came back in line a week or so later. Could have been bad strips, could have been antibodies, so they actually made me do I think 4 months of dual testing in the end before they were happy. The risk of that scenario recurring is manageable _for_ _me_ because (a) it was very noticeable as an odd reading, and (b) my dose is usually stable (with use of spinach / alcohol to manage INR variations ) - I basically won't take more than one small dose reduction before getting a venous cross-check.

Although I self-test now, I still have regular venous checks, six-monthly reviews, but the system lets me go in whenever I like (when blood room open) to get one done. I self-test weekly or more often if things (diet/illness/drugs/etc.) are changing, if I see my INR doing anything weird I go in for a vein check.

My INR is actually better controlled since moving to self-testing, time-in-range increased significantly in both my figures and clinic figures (clinic only want readings every two weeks usually, so I have more data). I still regard the vein value as the "real" INR, and the coaguchek tells me how that has changed since the last real reading, I am not sure I've found the "best" interval between vein checks yet, six months still feels a bit too long to leave it.

[Tofino5]

I hope you do well with this trial WendyWoo, and that you get very small variances! To have immediate feedback would be so helpful.

I'm not on warfarin now, but I trialed the machine early in my warfarin days. I have bad arm veins and needed hand sticks, and always had black and blue hands. I'm triple positive with high titres, and my INR was never stable in 10 1/2 years on warfarin. My variances were far too big, plus the results flipped around both higher and lower. My anticoagulant clinic was dead against the machines, so they were quite happy that I failed!

Good luck!!!