Well, there's a common condition called subclinical hypothyroidism which may be asymptomatic and harmless, or it may indicate thyroid disease and be accompanied

Well, there's a common condition called subclinical hypothyroidism which may be asymptomatic and harmless, or it may indicate thyroid disease and be accompanied by various non-specific symptoms. It's defined by slightly elevated TSH but normal T4 test results. Anybody with that condition would not be helped by what you are proposing. In general, it seems to me that you will get some false negatives when using a less sensitive test result to qualify a more sensitive test result.