Laboratory reference ranges for thyroid antibodies

[Greta]

I know I've bugged you guys with a million thyroid questions, but I have yet another one.   :blush:

 

My mom and I both went to walk-in labs for thyroid antibody tests because our doctors wouldn't order them for us (despite a family history, a diagnosis of hypothyroidism on her part, and some mild symptoms but "normal" numbers on my part).  Because we live in different states, we went to different labs.  

 

My lab said my TPOAb level was 16, and the reference range was 0-34, so mine was normal.

 

My mom's lab said her TPOAb level was 21, and the reference range was 0-9, so hers was high.

 

Those are some pretty different reference ranges.  I'm trying to figure out, does that mean that if I'd gone to her lab, mine would have been marked as high as well?  Or does that mean their equipment is so different than their lab might have measured mine at 4 or something instead of 16, and it would still be normal?  I did a quick google search and found reference ranges ranging from 4 to 35, with several in-between.  I'm so confused!  Should I be worried about my thyroid or not?  (My mom does have an appointment to see an endocrinologist.)

 

Thanks!

 

[Murphy101]

No. Thyroid ranges vary pending age and other factors.

[hornblower]

the lab results should give units, not just a number. Can you look again and post a unit? 

[Greta]

the lab results should give units, not just a number. Can you look again and post a unit?

Sorry, that was silly of me! Both labs were using IU/mL.

[hornblower]

Well, hopefully one of the experienced boardies chimes in. I had half my thyroid removed last year but I admit, I'm really handing over the *thinking* about my thyroid to my care team. I don't even really look at my lab results anymore. 


I thought that getting such different ranges like you report was weird but medscape says that different labs can use different methods/assay kits and get different readings. And that reference ranges are still arbitrary. 

I guess that explains why my doc required mine to be done at the same lab - I think here actually there is only a couple places that even do it so that at least keeps trend lines consistent.... 

https://www.medscape.com/viewarticle/452668_5

Fwiw, I think things like this is where you need an endocrinologist. I think interpreting lab values is not simple at all. 

[Twigs]

… medscape says that different labs can use different methods/assay kits and get different readings. And that reference ranges are still arbitrary. …

 

I'm a Medical Laboratory Scientist and this info is correct. It could be as simple as 1 machine is running at 37°C and the other is running at 20°C.

 

Also, each lab will run the statistics to generate its own normal range, Therefore I would expect each lab to have a different normal range.

 

Also, each lab may be running different testing kits and using different machines. All these variable influence the patient values and the normal ranges.

[Greta]

I guess that explains why my doc required mine to be done at the same lab -

 

Fwiw, I think things like this is where you need an endocrinologist. I think interpreting lab values is not simple at all.

 

  

 

Thank you, hornblower, this sounds like good advice to me!

 

 

I'm a Medical Laboratory Scientist and this info is correct. It could be as simple as 1 machine is running at 37°C and the other is running at 20°C.

 

Also, each lab will run the statistics to generate its own normal range, Therefore I would expect each lab to have a different normal range.

 

Also, each lab may be running different testing kits and using different machines. All these variable influence the patient values and the normal ranges.

Thank you so much for this explanation! I really appreciate it. I will trust that my results were normal, then, and I’m glad my mom is seeing an endo.