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. Author manuscript; available in PMC: 2018 Nov 28.
Published in final edited form as: Circulation. 2017 Oct 23;136(22):2100–2116. doi: 10.1161/CIRCULATIONAHA.117.028753

Table 2.

Definition of Subclinical Hypothyroidism and Atrial Fibrillation Events

Study Cohort TSH and fT4
Reference Range
Definition of Subclinical Hypothyroidism in IPD Analysis AF Events – Methods of Ascertainment

United States
Cardiovascular Health Study TSH 0.45–4.50 mIU/L, fT4 9–22 pmol/L TSH ≥4.5 mIU/L & TSH <20mIU/L, normal fT4 0.7–1.7 ng/dL (9–22 pmol/L) or missing fT4 (0/436, 0%) Self-report, annual ECGs, ICD-9 coded AF on hospital discharge
Health ABC Study TSH 0.1–4.4 mIU/L, fT4 10.3–23.2 pmol/L TSH ≥4.5 mIU/L & TSH <20mIU/L, normal fT4 0.8–1.8 ng/dL (10.3–23.2 pmol/L) or missing fT4 (195/270, 72%) * Minnesota-coded ECGs at baseline and at year 4 follow-up, ICD-9 coded ambulatory and inpatient AF diagnoses from CMS data
Osteoporotic Fractures in Men (MrOS) Study TSH 0.55–4.78 mIU/L, fT4 9–24 pmol/L TSH ≥4.5 mIU/L & TSH <20mIU/L, normal fT4 0.7–1.85ng/dL (9–24pmol/L) or missing fT4 (0/46, 0%) ECG at baseline, self-report, AF diagnoses from medical records every 4 months
Europe
Bari Study TSH 0.35–5.50 mIU/L, fT4 9–23.2 pmol/L TSH ≥4.5 mIU/L & TSH <20mIU/L, normal FT4 0.7–1.8 ng/dL (9–23.2 pmol/L) or missing fT4 (0/23, 0%) ICD-9 coded AF on hospital discharge
Leiden 85+ Study TSH 0.3–4.8 mIU/L, fT4 13–23 pmol/L TSH ≥4.5 mIU/L & TSH <20mIU/L, normal fT4 1.0–1.8ng/dL (13–23 pmol/L) or missing fT4 (1/27, 3.7%) Minnesota-coded annual ECGs
Study of Health in Pomerania TSH 0.25–2.12 mIU/L, fT4 8.3–18.9 pmol/L TSH ≥4.5 mIU/L & TSH <20mIU/L, normal fT4 0.64–1.47ng/dL (8.3–18.9 pmol/L) or missing fT4 (0/12, 0%) Minnesota-coded ECGs at baseline, year 5 and year 10 follow-up
Invecchiare in Chianti Study TSH 0.46–4.68 mIU/l, fT4 9.9–28.2 pmol/L TSH ≥4.5 mIU/L & TSH <20mIU/L, normal fT4 0.77–2.19ng/dL (9.9–28.2pmol/L) or missing fT4 (0/26, 0%) ECGs at baseline, 3 year, 6 year and 9 year follow-up
Rotterdam Study TSH 0.4–4.0 mIU/L, fT4 11–25 pmol/L TSH ≥4.5 mIU/L & TSH <20mIU/L, normal fT4 0.9–1.9ng/dL (11–25pmol/L) or missing fT4 (29/91, 31.9%) ECGs at baseline, year 2 and year 7 follow-up, ICD-10 coded AF diagnoses from GP records and hospital discharge
PROSPER Study TSH 0.45–4.50 mIU/L, fT4 12–18 pmol/L TSH ≥4.5 mIU/L & TSH <20mIU/L, normal fT4 0.9–1.4 ng/dL (12–18pmol/L) or missing fT4 (211/384, 54.9%) Minnesota-coded annual ECGs
EPIC-Norfolk TSH 0.4–4.0 mIU/L, fT4 9–20 pmol/L TSH ≥4.5 mIU/L & TSH <20mIU/L, normal fT4 0.7–1.6ng/dL (9–20 pmol/L) or missing fT4 (0/607, 0%) Self reported intake of drugs used for AF treatment at baseline (digitalis and VKAs), ICD-10 coded AF on hospital discharge
Australia
Busselton Health Study TSH 0.4–4.0 mIU/L, fT4 9–23 pmol/L TSH ≥4.5 mIU/L & TSH <20mIU/L, normal fT4 0.7–1.8ng/dL (9–23 pmol/L) or missing fT4 (1/ 37, 2.7%) Minnesota-coded ECGs at baseline and at year 14 follow-up

Abbreviations: AF, atrial fibrillation; ECG, electrocardiogram; EPIC, European Prospective Investigation of Cancer; fT4, free thyroxine; GP, general practitioner; ICD, International Statistical Classification of Diseases and Related Health Problems; IPD, individual participant data; PROSPER, Prospective Study of Pravastatin in the Elderly at Risk; TSH, thyroid stimulating hormone, VKA, vitamin K antagonist.

*

fT4 was measured only in participants with TSH ≥ 7.0 mIU/L or TSH in this cohort

fT4 was measured only in participants with TSH ≥4.5mIU/l in this cohort

HHS Vulnerability Disclosure