In case this is of interest… here are a few links about blood tests in general and thyroid tests in particular
Extract of the above article below, however I found the article as a whole interesting to read:
"Laboratories always indicate, for every requested parameter, a range of reference values. The norms are defined to include 95% of the "healthy" population within this reference range, with 2.5% of subjects above and 2.5% under the proposed range. It is simply a general rule!
… An excellent example of the inadequacy of relying on the reference values can be seen with Thyroid Stimulating Hormone (TSH)… A longstanding controversy with the standard ranges concerns the upper limit of references ranges for TSH, classically defined between 4 and 5. It now seems likely that the sample Caucasian population that was used to establish the "healthy" range of TSH was actually significantly "contaminated" by subjects with low-grade thyroid disease…
By introducing into the sample reference population a significant proportion of subjects who were slightly hypothyroid… the reference values were thus biased. Since then, calculations performed on a population pre-selected by a blood test and screened for auto-antibody carriers, and an ultrasound of the thyroid gland to detect goitre, resulted in quite different values. These results suggest that the upper limit for TSH should be brought down to 2.5 instead of the 4.5, which is still used to this day by most laboratories…"
And in the UK GPs won't diagnose hypothyroidism unless TSH comes up above 10...
Another link about what a joke blood tests can become depending on how they are used and what population the “normal ranges” are based on:
And another link. This Dr explains how hard it is for a Hashimoto patient to be diagnosed on the basis of “the TSH test”… it just makes no sense whatsoever: