The TSH
test, itself, is a very accurate
test... the problem is that it doesn't always tell you what you need to know, when it comes to thyroid, because TSH is a pituitary hormone, not a thyroid hormone.
When testing for thyroid conditions, you always need to test Free T3 and Free T4, which are the actual thyroid hormones, along with the TSH and many doctors, either don't know this or don't think it necessary. They think TSH is adequate.