Format

Send to

Choose Destination
PLoS One. 2018 Apr 30;13(4):e0196631. doi: 10.1371/journal.pone.0196631. eCollection 2018.

Initial evaluation of thyroid dysfunction - Are simultaneous TSH and fT4 tests necessary?

Author information

1
Department of General Internal Medicine, Inselspital, Bern University Hospital, University of Bern, Bern, Switzerland.
2
Institute of Primary Health Care (BIHAM), University of Bern, Bern, Switzerland.
3
Departments of Medicine and Epidemiology and Biostatistics, University of California, San Francisco, California, United States.
4
Service of Endocrinology, Diabetes and Metabolism, Lausanne University Hospital, Lausanne, Switzerland.
5
Applied Health Research Centre, Li Ka Shing Knowledge Institute of St Michael's Hospital, Institute of Health Policy, Management and Evaluation, University of Toronto, Toronto, Canada.
6
Department of Internal Medicine, Erasmus Medical Center, Rotterdam, the Netherlands.
7
Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia.
8
School of Population Health, The University of Western Australia, Crawley, Western Australia, Australia.
9
School of Women's and Infants' Health, The University of Western Australia, Crawley, Western Australia, Australia.
10
Diagnostica Stago, Doncaster, Victoria, Australia.
11
Medical School, University of Western Australia, Crawley, Western Australia, Australia.
12
UWA Centre for Medical Research, Harry Perkins Institute for Medical Research, Perth, Western Australia, Australia.

Abstract

OBJECTIVE:

Guidelines for thyroid function evaluation recommend testing TSH first, then assessing fT4 only if TSH is out of the reference range (two-step), but many clinicians initially request both TSH and fT4 (one-step). Given limitations of previous studies, we aimed to compare the two-step with the one-step approach in an unselected community-dwelling study population, and develop a prediction score based on clinical parameters that could identify at-risk patients for thyroid dysfunction.

DESIGN:

Cross-sectional analysis of the population-based Busselton Health Study.

METHODS:

We compared the two-step with the one-step approach, focusing on cases that would be missed by the two-step approach, i.e. those with normal TSH, but out-of-range fT4. We used likelihood ratio tests to identify demographic and clinical parameters associated with thyroid dysfunction and developed a clinical prediction score by using a beta-coefficient based scoring method.

RESULTS:

Following the two-step approach, 93.0% of all 4471 participants had normal TSH and would not need further testing. The two-step approach would have missed 3.8% of all participants (169 of 4471) with a normal TSH, but a fT4 outside the reference range. In 85% (144 of 169) of these cases, fT4 fell within 2 pmol/l of fT4 reference range limits, consistent with healthy outliers. The clinical prediction score that performed best excluded only 22.5% of participants from TSH testing.

CONCLUSION:

The two-step approach may avoid measuring fT4 in as many as 93% of individuals with a very small risk of missing thyroid dysfunction. Our findings do not support the simultaneous initial measurement of both TSH and fT4.

PMID:
29709030
PMCID:
PMC5927436
DOI:
10.1371/journal.pone.0196631
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Public Library of Science Icon for PubMed Central
Loading ...
Support Center