Search Results
Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam, The Netherlands
Search for other papers by Stan R Ursem in
Google Scholar
PubMed
Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam, The Netherlands
Amsterdam Reproduction & Development, Amsterdam, The Netherlands
Search for other papers by Anita Boelen in
Google Scholar
PubMed
Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam, The Netherlands
Search for other papers by Jacquelien J Hillebrand in
Google Scholar
PubMed
Amsterdam Public Health, Amsterdam, The Netherlands
Search for other papers by Wendy P J den Elzen in
Google Scholar
PubMed
Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam, The Netherlands
Amsterdam Reproduction & Development, Amsterdam, The Netherlands
Department of Laboratory Medicine, Endocrine Laboratory, Amsterdam UMC Location Vrije Universiteit Amsterdam, Boelelaan, Amsterdam, The Netherlands
Search for other papers by Annemieke C Heijboer in
Google Scholar
PubMed
Objective
International guidelines concerning subclinical hyperthyroidism and thyroid cancer advice absolute cut-off values for aiding clinical decisions in the low range of thyroid-stimulating hormone (TSH) concentrations. As TSH assays are known to be poorly standardized in the normal to high range, we performed a TSH assay method comparison focusing on the low range.
Methods
Sixty samples, selected to cover a wide range of TSH concentrations (<0.01 to 120 mIU/L) with oversampling in the lower range (<0.4 mIU/L), were used for the method comparison between three TSH immunoassays (Cobas, Alinity and Atellica). In addition, 20 samples were used to assess the coefficient of variation from duplicate measurements in these three methods.
Results
The TSH immunoassays showed standardization differences with a bias of 7–16% for the total range and 1–14% for the low range. This could lead to a different classification of 1.5% of all measured TSH concentrations <0.40 mIU/L measured in our laboratory over the last 6 months, regarding the clinically important cut-off value of TSH = 0.1 mIU/L. As the imprecision of the immunoassays varied from 1.6–5.5%, this could lead to a similar reclassification as the bias between immunoassays.
Conclusions
We established the standardization differences of frequently used TSH assays for the total and low concentration ranges. Based on the proportional bias and the imprecision, this effect seems to have limited clinical consequences for the low TSH concentration range. Nevertheless, as guidelines mention absolute TSH values to guide clinical decision-making, caution must be applied when interpreting values close to these cut-offs.
Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam, The Netherlands
Department of Clinical Chemistry, Endocrine Laboratory, Amsterdam UMC location University of Amsterdam, Amsterdam, The Netherlands
Search for other papers by Heleen I Jansen in
Google Scholar
PubMed
Search for other papers by Antonius E van Herwaarden in
Google Scholar
PubMed
Search for other papers by Henk J Huijgen in
Google Scholar
PubMed
Amsterdam Reproduction & Development Research Institute, Amsterdam, The Netherlands
Search for other papers by Rebecca C Painter in
Google Scholar
PubMed
Department of Clinical Chemistry, Endocrine Laboratory, Amsterdam UMC location University of Amsterdam, Amsterdam, The Netherlands
Search for other papers by Jacquelien J Hillebrand in
Google Scholar
PubMed
Department of Clinical Chemistry, Endocrine Laboratory, Amsterdam UMC location University of Amsterdam, Amsterdam, The Netherlands
Amsterdam Reproduction & Development Research Institute, Amsterdam, The Netherlands
Search for other papers by Anita Boelen in
Google Scholar
PubMed
Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam, The Netherlands
Department of Clinical Chemistry, Endocrine Laboratory, Amsterdam UMC location University of Amsterdam, Amsterdam, The Netherlands
Amsterdam Reproduction & Development Research Institute, Amsterdam, The Netherlands
Search for other papers by Annemieke C Heijboer in
Google Scholar
PubMed
Objective
Thyroid hormone measurements are often performed in pregnant women, as hypo- and hyperthyroidism during pregnancy can severely affect the fetus. Serum free thyroxine (fT4) measurements are well known for their analytical challenges, due to low serum concentrations and the subtle equilibrium between free and bound T4 (to thyroid-binding globulin (TBG), transthyretin and albumin). Pregnant women have high TBG concentrations due to an increase in human chorionic gonadotropin (hCG) and estrogen and lower albumin concentrations which change the equilibrium and may affect the validity of fT4 measurements in their samples. As accurate serum fT4 measurements in pregnant women are important for the long-term health of the fetus, we aimed to evaluate the accuracy of several fT4 immunoassays in the serum of pregnant women.
Methods
FT4 was measured in healthy controls and pregnant women using a candidate-reference method (LC-MS/MS) and five commercially available automated immunoassays (Alinity (Abbott), Atellica (Siemens), Cobas (Roche), Lumipulse (Fujirebio) and UniCel DXI (Beckman Coulter)). Method comparisons (Bland Altman plots and Passing and Bablok analyses) were performed.
Results
Serum samples from both healthy controls (n = 30) and pregnant women (n = 30; mean gestational age, 24.8 weeks) were collected. The fT4 immunoassays deviated +7 to +29% more from the LC-MS/MS in serum samples of pregnant women than healthy controls (falsely high).
Conclusions
Our results indicate that immunoassays overestimate fT4 in pregnant women, which might lead to an overestimation of thyroid status. Physicians and laboratory specialists should be aware of this phenomenon to avoid drawing false conclusions about thyroid function in pregnant women.
