Gestational age-specific reference ranges from different laboratories misclassify pregnant women's thyroid status
- Authors:
-
- Bliddal, Sofie ;
- Feldt-Rasmussen, Ulla ;
- Boas, Malene ;
- Faber, Jens ;
-
Juul, Anders
;
Close
0000-0002-0534-4350
Department of Clinical Medicine, Department of Clinical Medicine, Faculty of Health and Medical Sciences, Københavns Universitet - Larsen, Torben ;
- Precht, Dorthe Hansen
- Subtitle:
- comparison of two longitudinal prospective cohort studies
- DOI:
- 10.1530/EJE-13-0672
- Abstract:
- OBJECTIVES: Correct interpretation of thyroid status during pregnancy is vital to secure fetal development. Pregnancy-related changes in maternal thyroid status necessitate the use of gestational age-specific reference ranges. In this study, we investigated between-laboratory reproducibility of thyroid reference ranges in pregnant women. DESIGN: Comparison of two longitudinal prospective cohort studies including 255 (cohort 1) and 101 (cohort 2) healthy antibody-negative Danish pregnant women attending prenatal care at Copenhagen University Hospital. METHODS: Different immunoassays were used to measure thyroid hormone levels in the two cohorts. Thyroid hormone reference ranges were established for every 5 weeks of gestation. Differences between cohorts were explored through mixed-model repeated measures regression analyses. By applying reference ranges from one cohort to the other, the proportion of women who would be misclassified by doing so was investigated. RESULTS: TSH increased and free thyroxine (FT4) decreased as pregnancy progressed. Results indicated highly significant differences between cohorts in free triiodothyronine (F=21.3, P<0.001) and FT4 (F=941, P<0.001). TSH levels were comparable (P=0.09). Up to 90.3% of the women had FT4 levels outside their laboratory's nonpregnant reference range, and up to 100% outside the other cohort's gestational-age-specific reference ranges. Z-score-based reference ranges markedly improved comparison between cohorts. CONCLUSION: Even in the same region, the use of gestational-age-specific reference ranges from different laboratories led to misclassification. Up to 100% of maternal FT4 levels fell outside the other cohort's reference range despite similar TSH levels. In clinical practice, thyroid testing of pregnant women without adding method specificity to gestational age-dependent reference ranges will compromise patient safety.
- Type:
- Journal article
- Language:
- English
- Published in:
- European Journal of Endocrinology, 2014, Vol 170, Issue 2, p. 329-339
- Keywords:
- Adult; Diagnostic Errors; Female; Fluoroimmunoassay; Gestational Age; Humans; Longitudinal Studies; Luminescent Measurements; Pregnancy; Prospective Studies; Reference Values; Reproducibility of Results; Thyroid Diseases; Thyroid Function Tests; Thyroid Gland; Thyrotropin; Thyroxine; Triiodothyronine; Comparative Study; Journal Article; Research Support, Non-U.S. Gov't
- Main Research Area:
- Medical science
- Publication Status:
- Published
- Review type:
- Peer Review
- Submission year:
- 2014
- Scientific Level:
- Scientific
- ID:
- 256935607
