Blood tests from gp differ from medichecks

Latest results from gp that I had done Monday (same day as I had medichecks done). Medichecks was done at 8am and gp blood tests performed at 12pm.

CRP - <1mg (<5)

TSH 1.88 mU/L (0.27 - 4.20)

T4 12.9 pmol/L (11.0 - 25.0)

Ferritin 86 ug/L (15-300)

Medichecks completely different to these ranges! Both done early morning, I was also fasting.

[SeasideSusie Remembering]

AnxietySufferer92

Can you add the Medichecks results/ranges so we can see what the difference is. Each lab has it's own range (the numbers in brackets) so we have to work out percentages through range to compare results when ranges are different.

[Hidden in reply to SeasideSusie]

Done. Sorry about that. X

[SeasideSusie Remembering in reply to Hidden]

AnxietySufferer92

There will be differences because the tests weren't done at the same time, although you've said both done early morning you also said Medichecks was done at 8am and GP test at 12 noon.

The earlier the test the higher the TSH, see daily rhythms of thyroid hormones here, TSH is the first graph:

healthunlocked.com/thyroidu...

So that can explain the difference in your TSH:

Medichecks 8am - 3.29 (0.27-4.2)

GP Noon - 1.88 (0.27-4.2)

FT4 will be a bit higher at 8am than noon (second graph) and you have:

Medichecks test is 20% through range

GP test is 13.57% through range

Ferritin has been the subject of a recent investigation by Medichecks instigated by member jsy_girl and her latest post is here:

healthunlocked.com/thyroidu...

so we don't expect the ferritin tests to make much sense anyway but the difference in yours is:

Medichecks - 59.85% through range

GP - 24.91% through range

I've never had a ferritin test done the same day with both GP and private lab, the closest I've had is 2 months apart and the difference is frequently similar to this:

Medichecks - 45% through range

GP - 11% through range

GP doesn't normally test so I just use Medichecks now.

As for CRP, clearly your GP result shows the testing equipment isn't calibrated to measure below 1 which is why it just says <1, whereas the Medichecks equipment does measure lower so it's giving a more accurate measurement. It's not important anyway, it's very low which is good.

[jsy_girl in reply to SeasideSusie]

And if you ignore the range for ferritin which I do find odd because of the significant variation on the upper end of the scale, the actual numbers are some of the closest I’ve seen between the two. Typically Nhs result is lower. Makes sense to assume you’re somewhere between your NHS result and the medichecks result.

[tattybogle]

That's actually OK, and logical . TSH is naturally lower towards the afternoon than at 8am , so the lower GP number for TSH is probably explained by that. (or mostly anyway)

and the fT4 result is actually very similar in both when you adjust for the different lab ranges. (it's 20% in medichecks, and little under 20% in GP's, which is easily explained by T4 being produced in pulsatile fashion rather than a steady stream through the day )