Plasma Free T3 or Serum Free T3?

[SpringFairy]

My GP has always tested my 'Plasma Free' T4 & T3.

The latest results show my 'Serum Free' T3 & T4 levels

Edit. TSH is also a 'Serum-Free' test.

Can anyone explain the difference between them with regards to thyroid? They have different ranges & I'm a bit disappointed not to be able to compare them directly to my years of results. (Although I'm on T3 monotherapy, so actual results aren't so important anyway 😅)

cellgs.com/blog/serum-vs-pl...

[helvella Administrator Thyroid UK]

We rarely distinguish!

I think most are plasma as the tubes contain anti-clotting agents.

Ask A Scientist: What’s the Difference Between Serum and Plasma?

criver.com/eureka/ask-scien...

[SpringFairy in reply to helvella]

Thank you helvella. Good link 👍

***Serum is the liquid that remains after the blood has clotted***

***Plasma is the liquid that remains when clotting is prevented with the addition of an anticoagulant***

Because they have different ranges though, I've still given them new columns in my spreadsheet, so I can work out the %'s 😬🙄

[helvella Administrator Thyroid UK in reply to SpringFairy]

It sometimes feels that these things are done to confuse us. And it often works on me!

[SpringFairy in reply to helvella]

😂😂😂

Glad it's not just me. I'm only 9 months out of my decades long 'semi-comatose, no thyroid treatment life' & the tiniest things can make my brain spin!

Hopefully more months of T3 to the ole brain cell (s) will improve this.

Thank you helvella. Have a lovely weekend x