One blood draw - two different FT4 results

[Bearo]

At my recent blood test at the GP surgery the nurse obligingly filled my vial for me to send back to Monitor My health. So one early morning fasting blood draw went to two different labs but the ranges are the same:

TSH 0.14 (0.27-4.20) both labs

FT3 4.6 (3.1-6.8) 40.5% Monitor my health

FT4 15.9 (12-22) 39% MMH 18 (12-22) 60% local

11 Jan 2021. On 75mcg levo

I would invite comments on the results - but which results? Am I right in assuming T4 is normally higher in range than T3 so MMH is probably incorrect?

The GP gave me a lecture on how the thyroid works and told me my TSH was suppressed. He then asked me about my symptoms and as I said I don’t have tremors or palpitations he agreed to raise my dose to 100mcg rather than reduce it.it has taken me 12 months to achieve this dose, but as my TSH has been below 1 ever since I started on Levo, I’m lucky I’m not still on 50mcg.

I’m on my 4th day of 100mcg levo and I’m disappointed not to have the surge of energy I had for the first five days when I went up to 75mcg. Other than that I’ve never felt any different on levo. I think my dose for my weight is around 110mcg so maybe I’ll need another increase.

The GP who agreed that dose increase is retiring and suggested my next blood test be in three months, so he’ll have gone by then. I don’t know if I dare risk another NHS test giving them another opportunity to reduce my levo.

By the way, vitamins were tested in October

Vit D 92 Upped supplement to 5,000 iu

B12 348 Ngl Started Igennus a complex + 500 b12

Folate 14.6 (2.4-17.5)

Ferritin 72 (13-150) Added some meat to diet (was vege)

Stopped biotin a week before blood test.

All comments welcomed. Shouldn’t I have a bit more zing by now?

[helvella Administrator Thyroid UK]

Recently one member has posted several times because of inconsistencies in blood tests - in her case, ferritin tests.

This is her profile - you can read her posts:

healthunlocked.com/user/jsy...

I suggest that you consider contacting both laboratories and asking for their opinions on the very clear difference. At the least, it would be worth finding out which analyser/test kits they are using. Some are known to produce results which are somewhat out of step with others.

[Bearo in reply to helvella]

Thanks, Helvella, I will give MMH a call. Not sure about the lab at local hospital.

[tattybogle]

Yours is not the only example i've come across on here in the last 12 months of a 'twin' test giving slightly different results at different labs. I've decided that the process for coming up with the result is probably pretty complicated , and i bet that if more of us did the same kind of twin testing experiment to compare, we would see many many more examples of variations in result.

My conclusion is that actually we should take all blood results with a pinch of salt , and pay more attention to trends of results over time than to any individual result.

see these i found ;

pubmed.ncbi.nlm.nih.gov/216...

pubmed.ncbi.nlm.nih.gov/157...

I don't really understand anything about lab testing processes for fT4/3 , but i know enough to know it's not as simple or accurate as we'd like to think it is.

[Bearo in reply to tattybogle]

Thanks - it makes sense there’s a percentage variation for different lab techniques.I wonder if anyone can comment on my conversion T4 to T3 given either of these sets of results?

[SeasideSusie Remembering in reply to Bearo]

Bearo

Am I right in assuming T4 is normally higher in range than T3 so MMH is probably incorrect?

Optimally medicated on Levo and having good conversion, FT4 and FT3 would be more or less in balance.

I wonder if anyone can comment on my conversion T4 to T3 given either of these sets of results?

It looks like you only have FT4/FT3 results from MonitorMyHealth and according to those your conversion is very good:

FT3 4.6 (3.1-6.8) 40.5% Monitor my health

FT4 15.9 (12-22) 39% MMH

Did the local lab do FT3 when doing FT4 and you've missed it out?

[Bearo in reply to SeasideSusie]

No, I got the MMH test cos I knew GP wouldn’t be testing T3. But I had a different T4 result from GPs test, with T4 60% in range despite the sample coming from the same blood draw.

[Bearo in reply to Bearo]

Oh, I see what you mean, look at MMH for T4 and T3, rather than trying to shoehorn another lab’s T4 result into the picture, as I was considering. No wonder I didn’t follow science at school!

[SeasideSusie Remembering in reply to Bearo]

Yes, that's right. Don't mix and match results from different labs even when reference ranges are the same and it's blood from the same draw

[MMaud]

Bearo - was your blood draw venous blood, from your arm/hand? The MMH is designed for capillary samples, via a finger prick test.

For this test, I don't know if it makes a difference, but for some dynamic/variable tests it can make a difference.

I'll be interested to hear the feedback you receive.

A couple of months ago, I had two lots of bloods done on the same day, from the same blood draw. One set was for my GP, and the other in preparation for a hospital clinic appointment. Most tests differed, but there were a couple of duplicates, including Vit D.

For the VitD results there was a variance of almost 15%. My GP just didn't address it, when asked, and the hospital doctor basically just gave me the "trust me , I'm a Doctor" speak.

You might find this interesting: bmj.com/content/368/bmj.m149

[Bearo]

Good point MMaud, it was a venous draw into the vial designed for finger prick. I didn’t think about that making a difference. I might get in touch with MMH and ask them about it. I’ll post their reply if they say something definitive.

[nellie237]

I watched something earlier this evening on you tube where it was mentioned that the only standardised test around the world is the HBA1C (Diabetes monitoring).