FT3 reference range medichecks

[Craigd101]

Hi,

I had my latest blood test done with medichecks using the finger prick method at home, as my GP cancelled my appointment due to coronavirus. My FT3 result is 4.5 pmol/L, which is exactly the same as when I last tested with my GP in January. I was expecting this as I have not changed anything.

What has confused me slightly is the reference range: my GP reference range for FT3 is 4.00 - 6.80, whereas with medichecks the range is 3.10 - 6.80. Both measures are pmol/L. With my FT3 at 4.5, the medichecks scale obviously puts me further through the range than my GPs scale, and makes my result look somewhat better.

The TSH & FT4 ranges are identical.

I've seen different ranges before, but not a wider range using the same unit of measure. Has anyone come across this? Which scale is more typical?

Thanks

Craig

[SeasideSusie Remembering]

Craigd101

Ranges tend to be based on local population and also the machines used for testing come into it.

Private testing companies tend to use the same range, at least Blue Horizon, Medichecks and Thriva do but they also use the same couple of testing labs (usually County Pathology or The Doctor's Laboratory)

Our hormone levels aren't static, they will vary depending on time of day, when we took our last dose of thyroid meds, how much conversion of T4 to T3 had taken place at the time of the blood draw, etc. So we don't expect them to be exactly the same every time we test, even if testing conditions are identical each time.