Reference levels for serum thyroid function tests of diagnostic and prognostic significance

Area of Science:

• Endocrinology
• Clinical Chemistry
• Epidemiology

Background:

• A debate persists regarding the optimal upper reference limit for thyrotropin (TSH).
• Existing research relies on cross-sectional data, limiting understanding of prognostic implications.
• Establishing TSH reference values with both diagnostic and prognostic significance is crucial.

Purpose of the Study:

• To determine serum thyroid function test reference values with diagnostic and prognostic significance.
• To investigate differences in TSH reference intervals based on event-free versus general populations.

Main Methods:

• Utilized prospective, population-based data from the Study of Health in Pomerania (SHIP).
• Analyzed data from 1203 subjects without pre-existing thyroid disorders, with a 5-year follow-up.
• Compared reference intervals derived from the whole reference population versus an event-free reference population.

Main Results:

• Identified notable differences in TSH reference intervals between the two populations.
• The upper TSH reference value was 7.6% lower (1.95 mIU/l) in the event-free population.
• Serum FT3 and FT4 reference intervals showed no substantial differences between populations.

Conclusions:

• The current upper TSH reference value may be higher than recommended when prognostic significance is considered.
• Defining TSH reference ranges requires incorporating both diagnostic accuracy and prognostic value.
• Further research is needed to refine TSH reference intervals for improved thyroid disorder management.