Current utility of first‐line freeT4 (FT4) and thyroid stimulating hormone (TSH) in screening for central hypothyroidism
Authors' conclusion
Although low-FT4 is a common laboratory finding, the incidence of central hypothyroidism remains rare. With the currently increased rates of thyroid testing and increased use of medications that decrease FT4, low-FT4 has a much lower predictive value for central hypothyroidism than previously reported. Thyroid screening strategies will need to balance the yield from first line TSH and FT4 testing with the cost of investigating individuals with non-pathological laboratory abnormalities.
Study context
- Population
- Patients aged ≥16 years with decreased FT4 and inappropriate TSH (low-FT4), All-Wales laboratory information system
- Outcome
- Incidence of central hypothyroidism among patients with low-FT4; utility of first-line TSH and FT4
- Follow-up
- 1-year
Methodological detailsAll-Wales laboratory information system
- All-Wales laboratory information system
Main finding
As reported in the abstract
New cases of central hypothyroidism in two health boards
15
Incidence of central hypothyroidism
2 cases/100,000 population/year
PPV of low-FT4 for central hypothyroidism
2%-4%
Observational data: associations, not effects.
Further findings
Incidence of low-FT4 by FT4 assay method · 1-year
- Incidence of low-FT4 varied by FT4 assay method (range)
- 98-301 cases/100,000 population/year
Low-FT4 in primary care thyroid tests (cross-section)
- Low-FT4 detected in all thyroid tests, with assay-related differences in detection rates
- 0.5%
Original publication
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