In:
Annals of Clinical Biochemistry: International Journal of Laboratory Medicine, SAGE Publications, Vol. 50, No. 6 ( 2013-11), p. 595-602
Abstract:
Trimester-specific reference intervals (RIs) for thyroid function tests are lacking for Beckman Dxl 800 analysers. We aimed to establish RIs for thyroid stimulating hormone (TSH), free thyroxine (fT4) and to track intraindividual changes in thyroid function throughout pregnancy. Methods One hundred and thirty healthy women without antithyroid peroxidase antibodies were followed longitudinally. Thyroid function was determined at trimester-1 (T1): 9–13 weeks; trimester-2 (T2): 22–26 weeks; trimester-3 (T3): 35–39 weeks and postpartum (PP): 8–12 weeks. A subgroup ( n = 47) was used to track intraindividual changes using PP as non-pregnant state (baseline). Results For trimesters 1–3, TSH (median (2.5th, 5th, 95th and 97.5th percentile)) was 0.77 (0.03, 0.05, 2.33, 3.05), 1.17 (0.42, 0.47, 2.71, 3.36) and 1.35 (0.34, 0.42, 2.65, 2.83) mIU/L, respectively. Free T4 (mean (95%CI)) was 10.7 (5.9–15.5), 8.1 (4.9–11.3), 7.8 (4.5–11.0) pmol/L, respectively. In T2 and T3, 36% and 41% of the fT4 values, respectively, fell below the non-pregnancy lower normal limit. In the subgroup assessed for longitudinal changes, of the women with baseline TSH ⩽ median, 71–75% remained at or below the corresponding median for trimesters 1–3. Of the women with baseline fT4 ⩽ median, 69–81% also remained at or below the corresponding median for trimesters 1–3. High correlation was observed at different trimesters and baseline for TSH (Spearman’s r: 0.593–0.846, P 〈 0.001) and for fT4 ( r: 0.480–0.739, P 〈 0.001). Conclusions Use of trimester-specific RIs would prevent misclassification of thyroid function during pregnancy. In the majority of women, TSH and fT4 tracked on the same side of the median distribution, from a non-pregnant baseline, throughout pregnancy.
Type of Medium:
Online Resource
ISSN:
0004-5632
,
1758-1001
DOI:
10.1177/0004563213486450
Language:
English
Publisher:
SAGE Publications
Publication Date:
2013
detail.hit.zdb_id:
2041298-8
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