# Different reference ranges of thyroid antobodies

This is related to the following thread:

http://health.stackexchange.com/questions/3312/tpo-thyroid-peroxidase-antibodies-reference-range-change

I have a question regarding the reference ranges of THYROGLOBULIN ANTIBODIES and THYROID PEROXIDASE ANTIBODIES. A recent test of a one of my friend's gave:

• THYROGLOBULIN ANTIBODIES 3 IU/mL reference range less than 1 IU/mL
• THYROID PEROXIDASE ANTIBODIES 19 IU/mL reference range less than 9 IU/mL

I have found conflicting info about the reference ranges for the two antibodies, for example, Medscape shows the reference ranges are 20 IU/mL and 35 IU/mL respectively.

Let me take THYROID PEROXIDASE ANTIBODIES to ask the question: if the same blood sample is sent to two labs the same day with different reference ranges, one is 35 IU/mL, one is 9 IU/mL. 35 is about 4 times of 9, can I say that the result value of the THYROID PEROXIDASE antibody in the lab with range 35 will be roughly 4 times of the result value at the lab of reference range 9? For example, the result value of the antibody at the lab of reference range 9 IU/mL turns out to be 19 IU/mL, then the same blood sample tested in the lab with range 35 should be roughly 4 times of 19, which is about 76 IU/mL? That way, the ratio of the result value to the reference range will be roughly 2 for both labs, i.e. 19/9, 76/35 are both roughly 2.

Or, I am completely wrong, the result value at the two labs should be roughly the same value, in the above mentioned example, both should be approximately 19 IU/mL? But then there is a problem for diagnosis, because one lab says it is within normal range, one says it is beyond normal range.