Gestational age-specific reference ranges from different laboratories misclassify pregnant women's thyroid status: comparison of two longitudinal prospective cohort studies
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Gestational age-specific reference ranges from different laboratories misclassify pregnant women's thyroid status : comparison of two longitudinal prospective cohort studies. / Bliddal, Sofie; Feldt-Rasmussen, Ulla; Boas, Malene; Faber, Jens; Juul, Anders; Larsen, Torben; Precht, Dorthe Hansen.
I: European Journal of Endocrinology, Bind 170, Nr. 2, 02.2014, s. 329-339.Publikation: Bidrag til tidsskrift › Tidsskriftartikel › Forskning › fagfællebedømt
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TY - JOUR
T1 - Gestational age-specific reference ranges from different laboratories misclassify pregnant women's thyroid status
T2 - comparison of two longitudinal prospective cohort studies
AU - Bliddal, Sofie
AU - Feldt-Rasmussen, Ulla
AU - Boas, Malene
AU - Faber, Jens
AU - Juul, Anders
AU - Larsen, Torben
AU - Precht, Dorthe Hansen
PY - 2014/2
Y1 - 2014/2
N2 - 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.
AB - 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.
KW - Adult
KW - Diagnostic Errors
KW - Female
KW - Fluoroimmunoassay
KW - Gestational Age
KW - Humans
KW - Longitudinal Studies
KW - Luminescent Measurements
KW - Pregnancy
KW - Prospective Studies
KW - Reference Values
KW - Reproducibility of Results
KW - Thyroid Diseases
KW - Thyroid Function Tests
KW - Thyroid Gland
KW - Thyrotropin
KW - Thyroxine
KW - Triiodothyronine
U2 - 10.1530/EJE-13-0672
DO - 10.1530/EJE-13-0672
M3 - Journal article
C2 - 24277773
VL - 170
SP - 329
EP - 339
JO - European Journal of Endocrinology
JF - European Journal of Endocrinology
SN - 0804-4643
IS - 2
ER -
ID: 120842300