Distribution of thyroid diseases and evaluation of laboratory parameters used in their diagnosis.

A retrospective rationalization of commonly performed tests and procedures for the assessment of patients with suspected thyroid disease was attempted. The final diagnosis, in 392 consecutive new referrals to a central thyroid clinic, was primarily established by combined criteria of clinical/scintigraphic/cytopathologic findings. Detailed statistical analysis and evaluation of the accumulated data have demonstrated that: (a) only 15.8% of patients exhibited measurable thyrometabolic disturbances, thus indicating a rather limited scope for the application of laboratory tests in screening for thyroid diseases; (b) the measurement of serum total thyroxine with the thyroid hormone uptake test and the derivation of the free thyroxine index constitute, at present, the most appropriate initial in vitro laboratory procedure for assessing thyrometabolic function; and (c) recently available innovative methods for estimating serum levels of free thyroid hormones have no advantages over established assays.