Home blood testing

[Bunny12345678]

Has anyone found home blood testing finger prick tests to be any less accurate than venous samples please? I've just found that Superdrug offer a good value service you see and wondered if to try it for IF testing???

[fbirder]

Why do you want an IF test?

Unless it's out of personal curiosity I wouldn't bother.

If it tests positive then you know you have PA. But that wouldn't persuade most GPs, who don't trust anything not done by the NHS.

If it tests negative then you might have PA.

Either way, having PA or not having PA should make no difference to your treatment.

[FlipperTD]

I realise that I'm spouting the old-fashioned scientist's approach, but whilst fingerprick tests work, venous blood tests generally work better. A decent venous sample taken by a competent phlebotomist and analysed promptly by a UKAS certified laboratory is generally capable of generating a more reliable result, and allows the lab to perform repeats or other confirmatory tests, whereas a fingerprick sample might not. It also allows the sample to be 'captured' into the system, and should ensure optimum storage conditions, which can make a considerable difference.

IF antibody tests can be troublesome enough on good, regular, venous samples, so I would opt for a venous sample every time if possible.

[helvella in reply to FlipperTD]

Over on the Thyroid UK forum, many people regularly use these finger-prick tests.

We sometimes see people who had both finger-prick and venous tests done at effectively the same time. For example, do a finger-prick tests then go to the GP and end up having a venous draw. Then at least some overlap of tests done.

Sometimes they are within an ace of each other. Certainly no further apart than two venous tests might have been.

Sometimes there are bigger differences but often there is an explanation other than finger-prick versus venous. For example, if the labs use different reference intervals, you'd probably expect the numerical values to be different.

I think most people would rather the greater certainty of a venous draw. They'd also prefer to have the sample at the lab as fast as possible. But I have become quite comfortable with finger-prick testing for many things.

For some reason, folate seems especially prone to getting reported as a failure from a finger-prick test even when every other test was OK.

(I have personally had blood spoiled before a test was done even when the draw was done within the phlebotomy unit of a hospital lab.)

[fbirder in reply to helvella]

I believe that the folate test is particularly prone to errors caused by haemolysis of the sample - where the red cells burst. This is more likely on a finger-prick sample. Other analyses may be the same.

[helvella in reply to fbirder]

Thanks - I did suspect something like that - good to have more detail.

[FlipperTD in reply to helvella]

Fbirder is absolutely right. Red cells are particularly rich in folate, and red cell folate is considerably more stable than serum folate. Haemolysis due to any reason is an issue, and squeezing the finger to get the sample doesn't help. Using smaller needles, or taking longer to get the sample, ditto. Storage is the enemy of a few analytes, but if you find a test that works reliably, that's fair enough. Potassium is another problem. Red cells are potassium-rich, and whenever there's a recall for a 'failed' potassium test, it's fairly likely that it's due to either the phlebotomy technique, or the storage & transport of the sample, and not the laboratory. It may be that the laboratory methods used on finger prick samples my be different too, so separate reference ranges my be valid.

[Bunny12345678 in reply to FlipperTD]

Thankyou for everyone's advice