Is finger prick blood testing accurate?

It's not me dissing finger prick testing here as I myself have used Blue Horizon and Medichecks over the last year for thyroid testing and my gp happily accepts them but I'm not sure he realises they're a finger prick result.

Anyway a friend of mine messaged me today saying she wouldn't trust them as she had read only that they are not consistent or accurate against an NHS vein blood test and results can be less accurate. Now this concerned me because I relied on Blue Horizon and Medicheck last year to get early morning thyroid testing so that my gp would diagnose me. I had NHS results from the summer before where my tsh was 5.35, ft4 10.2. Both borderline and my gp told me I was fine despite my fatigue. He went on to test me for all kinds of other things and ignoring the thyroid. It led to me being dragged to the clinic often for more appointments and tests and one day I was so fatigued and ill I had a severe panic attack during the a blood test which led to me developing a fear of blood tests and appointments there. I was so fatigued and ill I just couldn't do it anymore.

As of January 2016 after seeking advice here I used Blue Horizon and Medicheck for blood tests via a finger prick testing service. My tsh was 6.8 in January last year, 7.4 by march and 9.28 by May. I was then given treatment. I continue to use Medicheck to monitor my thyroid.

Last November my gp ran a full sweep of NHS bloods at my house. My fatigue wasn't lifting so he thought it was best to do a full MOT. All ok other than 1 glucose raised but hba1c ok and sodium ran low at 129, should have been at least 133. I found the test so anxiety provoking that I said seeing as I was due my thyroid test the week after with Medicheck i would repeat the sodium with them as he was concerned. The range with them was 135-145 and it came in at 138. Gp was pleased.

In January this year he said he wanted to repeat he sodium and hba1c about march time but seeing as now I've this huge phobia I again said I'd add them to my thyroid that was due in March too. It ended up cheaper to do their essentials blood test for £69 than pay individual for the 2 tests he wanted repeating. The essentials test is a full blood count, liver and kidney function, gout, cholesterol and hba1c oh and a full iron check. It came back my liver AST level was 0.5 over range and ALT 0.1. They've always been normal. Gp wants them repeating in 3 months but isn't worried. My serum iron was out by 6 but as my transferrin and ferritin levels were ok he wasn't worried. My hemoglobin was 15.5, highest it's ever been but gp said it was ok. My fbc was ok but my neutrophils ran low at 1.6 (range 2-7.5) and the Lymphocytes were 3.98 (range 1.2-3.65). He just said to repeat in 3 week.

I've repeated them and the neutrophils thankfully have come up to 1.8 but lymphocytes have continued to rise to 4.45. Gp isn't worried about them as I have bad adult acne at present but he's worried about the neutrophils stop being low despite them rising so he's written to a haemotologist for advice.

It's all set my anxiety racing i case I have something more sinister after googling lymphocytes and why they raise.

My friend knows I rely on the private results due to my blood test phobias and I have had a lot of anxiety issues since being hypo but now I'm questioning was I ever hypo, what if what she says is right and the finger prick bloods aren't accurate at all. How can the companies sell these tests if they aren't as accurate as an NHS vein test? She said she tested her thyroid with medicheck 2 days after an NHS test and it was 2 points higher on the finger prick test despite doing it fasted and at the same time of the morning. Her mum tested her cholesterol and it was high so she saw her gp who tested it and told her it was normal.

So now I'm worried was my thyroid ever needing Levo and is it why I'm struggling with fatigue and ill health most days? I now feel an idiot I've relied on these tests the last few months for my MoT too and it's come back with some worrying white cell results yet November it was fine and I didn't even need to repeat the fbc I just did as it was included in the cheaper test. I never expected any results to be out as they weren't really last year.

Has anyone else used these tests for other tests other than thyroid? Can anyone reassure me? I have health issues being investigated and I'm now worried the tests I've done aren't even accurate and I'm worried I've sent my gp results that aren't even accurate. Also worried can I be sure my sodium has raised and the hba1c repeat test was normal. It was normal on the NHS at 35 and Medicheck 34, and last spring 35. So for me they do tally up. Also my fbc done in march was done at County Pathology but the bloods done 2 weeks ago were at a lab in Manchester and the results were pretty dead on the same other than the 2 white cells slightly different.

It's just set my mind worrying and I wish I wasn't told this as it's made me doubt my tests and whether I should even have taken Levo.

Thank you


23 Replies

I have used medichecks and BH tests within 30 mins of Nhs bloods and results came out almost identical. Both the companies do testing for private hospitals. I will only do my annual TSH with nhs now to keep go happy. I feel more in control when IcN choose time and day of test and get the results direct to me. NHS has never tested my T3!

Thank you Crimple.

Can I ask we're your medicheck and bh the finger prick testing?

Even the normal blood tests can be inaccurate. Starting from handling them. It's not exact numbers , more so estimation as modern quick tests estimate the amount of hormones but fail to exclude all possible factors that affect test results.

Were her results in same range, was it two points in same range? TSH , fT4 or fT3? Same test method, same machinery?

No different to the NHS range which is what I tried to explain also that results differ range to range but she doesn't believe results differ if there's a different range used so I think that's why she was concerned about the accuracy of finger prick testing.

Well that's her problem if she doesn't believe results can differ despite different range :D or different method or machinery.

Maybe she had inaccurate test result from either one as it could happen for example if the samples are not handled correctly. We do not know.

But generally finger prick tests are safe and accurate. They are proved to be accurate.

Your TSH was high on NHS test was it? And ft4 low?

I the NHS in august 2015 my tsh was 5.35 (0.35-5.5( and ft4 10.2 (7-17). I did private from January 2016.

So, you had high TSH. I can't see what type of failure in finger prick testing would cause consistent increase in test results as your TSH kept steadily rising.

But if you are unsure you could go off of levo and get tested again after six months. But is that something you want to do?

No I'd not do that as I'm not as ill as I was before Levo. My tsh was high on the NHS but I did an afternoon test 3 months after it on the NHS where my tsh was 3 but ft4 was still low around 10. I then went private doing Blue Horizon tests and it steadily climbed from 6.8 to 9.28 from January to March.

That afternoon test we can ignore :)

But if you can't trust finger prick testing then you have to be brave and get tested at laboratory to get peace of mind unless you can organise get blood drawn at home early.

I did trust them until she cast the doubt lol!! Otherwise I'd never have taken Levo.

They are accurate if enough blood is delivered.

Company called theranos mentioned in the article claimed one drop is enough which was proven wrong.

I provide about 10 drops in a tube for a full blood count which includes about 10 results within the fbc.

So that's enough for accurate result!

That's what I thought, but my friend said she would only trust 10 drops if it was being used for 1 single result not one like a full blood count. Urgh it made me worry and doubt all the tests I had for thyroid etc

But thank you Justine. You've helped put my mind at rest. I was so upset yesterday after the doubt being cast because I've relied on these tests and I am struggling with chronic fatigue right now. My health is always so up and down with the fatigue so that doubt just made me worry about my fatigue more.

I know and I understand your worry.

But finger prick tests are accurate and reliable as normal blood test.

I had 16 tubes of blood drawn and 42 testes ran from it. It's not much more blood in the end taken that way as there can be very little blood in one tube and multiple tests taken .

They just take a bit more as they save up some in case retest is needed if you get weird results.

Thank you Justine. I appreciate you reassuring me and understanding why I was so worried about tests not being accurate.

Well i am always a bit sceptical when I have my blood drawn as I can't see is it handled properly! Lol. But can't do much but trust that it's done correctly.

I doubted finger prick testing too, but it was very consistent with normal blood test so I figured it's all good!

We just have to trust.

I agree. My recent full blood count was done in March and sent to a lab in the south of England and the repeat test 5 weeks later sent to a private lab in the north of England and both results were identical other than the 2 white cells were slightly different but they both picked up the 2 cells that were abnormal. So I know they must be accurate.

It was her tsh 2 points higher than NHS tsh

TSH can vary throughout the day, which probably explains it.

She did the test at the same time apparently as the NHS just 2 days later.

Yep. But TSH can naturally vary - not only during the day but over any number of days.

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