Ft4 range different labs


I was just wondering if the Ft4 ranges from different labs differ the same way as tsh ranges. I mean like the upper limit for Tsh is different because of new guidelines. That is they lowered the upper limit to be able to diagnose earlier in some countries. Is it the same way with ft4? Some labs have narrow ranges (10-19.5) and some much broader (9-23). Does anybody know? Sorry if I'm not making much sense but it's hard to explain what I mean...

5 Replies

I understand what you mean, but I'm pretty sure their aim is not to be able to diagnose more people! They would prefer to diagnose less people if they could!

No, it's not really the same. A TSH is always a TSH and, although they set all sorts of weird and wonderful ranges - getting higher and higher in the UK, unlike some other countries - you are, nevertheless, hypo as soon as your TSH hits 3.

With the Frees, the range is set by the machine that does the analysis. Different machines are calibrated to different ranges, and you always have to analyse the result using the range for the machine the test was done on. They are not interchangeable, I'm afraid. :)

I think you might be right! It seems, sometimes, like they don't want you to feel well. I'm seeing my doctor tomorrow and he was supposed to call me today but another one did and he said to reduce my levo. (I have just increased it directly after my bloodtest because I was feeling dreadful) Wouldn't give me the numbers either. :-(

But if that is the case with the calibration how can the range be wider?

If you're in the UK, then the doctor that refused to give you your numbers, is breaking the law. You have a legal right to your blood test results, under the 1998 Data Protection Act. Ring the receptionist and ask her.

The range is based on the local population. That's all I can tell you. But, I believe either helvella or diogenes has written a post about how they fix the ranges. So, if you have a look through their profiles, you might find it. Or, perhaps someone who knows more about it will come along and reply! :)

I am, I hope my ordinary doc will give them to me tomorrow though. AND increase my meds.

I'll keep my fingers crossed for you!

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