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  • Author: Annemieke C Heijboer x
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Anita Boelen Endocrine Laboratory, Department of Laboratory Medicine, Amsterdam UMC, location University of Amsterdam, Amsterdam, The Netherlands
Amsterdam Gastroenterology Endocrinology Metabolism, Amsterdam, The Netherlands
Amsterdam Reproduction & Development Research Institute, Amsterdam, The Netherlands

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Nitash Zwaveling-Soonawala Amsterdam Gastroenterology Endocrinology Metabolism, Amsterdam, The Netherlands
Department of Pediatric Endocrinology, Emma Children’s Hospital, Amsterdam UMC, location University of Amsterdam, Amsterdam, The Netherlands

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Annemieke C Heijboer Endocrine Laboratory, Department of Laboratory Medicine, Amsterdam UMC, location University of Amsterdam, Amsterdam, The Netherlands
Amsterdam Gastroenterology Endocrinology Metabolism, Amsterdam, The Netherlands
Amsterdam Reproduction & Development Research Institute, Amsterdam, The Netherlands
Endocrine Laboratory, Department of Laboratory Medicine, Amsterdam UMC, location Vrije Universiteit Amsterdam, Amsterdam, The Netherlands

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A S Paul van Trotsenburg Amsterdam Gastroenterology Endocrinology Metabolism, Amsterdam, The Netherlands
Department of Pediatric Endocrinology, Emma Children’s Hospital, Amsterdam UMC, location University of Amsterdam, Amsterdam, The Netherlands

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Thyroid hormone (TH) is indispensable for brain development in utero and during the first 2–3 years of life, and the negative effects of TH deficiency on brain development are irreversible. Detection of TH deficiency early in life by neonatal screening allows early treatment, thereby preventing brain damage.

Inborn shortage of TH, also named congenital hypothyroidism (CH), can be the result of defective thyroid gland development or TH synthesis (primary or thyroidal CH (CH-T)). Primary CH is characterized by low blood TH and elevated thyroid-stimulating hormone (TSH) concentrations. Less frequently, CH is due to insufficient stimulation of the thyroid gland because of disturbed hypothalamic or pituitary function (central CH). Central CH is characterized by low TH concentrations, while TSH is normal, low or slightly elevated.

Most newborn screening (NBS) programs for CH are primarily TSH based and thereby do not detect central CH. Only a few NBS programs worldwide aim to detect both forms of CH by different strategies. In the Netherlands, we have a unique T4–TSH–thyroxine-binding globulin (TBG) NBS algorithm for CH, which enables the detection of primary and central CH.

Although the necessity of central CH detection by NBS is still under debate, it has been shown that most central CH patients have moderate-to-severe hypothyroidism instead of mild and that early detection of central CH by NBS probably improves its clinical outcome and clinical care for central CH patients with multiple pituitary hormone deficiency. We are therefore convinced that detection of central CH by NBS is of utmost importance.

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Stan R Ursem Department of Laboratory Medicine, Endocrine Laboratory, Amsterdam UMC Location University of Amsterdam, Meibergdreef, Amsterdam, The Netherlands
Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam, The Netherlands

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Anita Boelen Department of Laboratory Medicine, Endocrine Laboratory, Amsterdam UMC Location University of Amsterdam, Meibergdreef, Amsterdam, The Netherlands
Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam, The Netherlands
Amsterdam Reproduction & Development, Amsterdam, The Netherlands

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Jacquelien J Hillebrand Department of Laboratory Medicine, Endocrine Laboratory, Amsterdam UMC Location University of Amsterdam, Meibergdreef, Amsterdam, The Netherlands
Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam, The Netherlands

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Wendy P J den Elzen Department of Laboratory Medicine, Laboratory Specialized Diagnostics & Research, Amsterdam UMC location University of Amsterdam, Meibergdreef, Amsterdam, The Netherlands
Amsterdam Public Health, Amsterdam, The Netherlands

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Annemieke C Heijboer Department of Laboratory Medicine, Endocrine Laboratory, Amsterdam UMC Location University of Amsterdam, Meibergdreef, Amsterdam, The Netherlands
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

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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.

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Heleen I Jansen Department of Clinical Chemistry, Endocrine Laboratory, Amsterdam UMC location Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam, The Netherlands
Department of Clinical Chemistry, Endocrine Laboratory, Amsterdam UMC location University of Amsterdam, Amsterdam, The Netherlands

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Antonius E van Herwaarden Radboud University Medical Center, Department of Laboratory Medicine, Nijmegen, The Netherlands

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Henk J Huijgen Department of Clinical Chemistry, Red Cross Hospital, Beverwijk, The Netherlands

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Rebecca C Painter Department of Obstetrics and Gynaecology, Amsterdam UMC Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
Amsterdam Reproduction & Development Research Institute, Amsterdam, The Netherlands

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Jacquelien J Hillebrand Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam, The Netherlands
Department of Clinical Chemistry, Endocrine Laboratory, Amsterdam UMC location University of Amsterdam, Amsterdam, The Netherlands

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Anita Boelen 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

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Annemieke C Heijboer Department of Clinical Chemistry, Endocrine Laboratory, Amsterdam UMC location Vrije Universiteit Amsterdam, Amsterdam, The Netherlands
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

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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.

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Kevin Stroek Endocrine Laboratory, Department of Clinical Chemistry, Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands

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Annemieke C. Heijboer Endocrine Laboratory, Department of Clinical Chemistry, Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands
Endocrine Laboratory, Department of Clinical Chemistry, Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam UMC, Vrije Universiteit, Amsterdam, The Netherlands

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Marja van Veen-Sijne Endocrine Laboratory, Department of Clinical Chemistry, Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands

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Annet M. Bosch Division of Metabolic Disorders, Department of Pediatrics, Emma Children’s Hospital, Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands

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Catharina P.B. van der Ploeg Department of Child Health, Netherlands Organization for Applied Scientific Research TNO, Leiden, The Netherlands

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Nitash Zwaveling-Soonawala Department of Paediatric Endocrinology, Emma Children’s Hospital, Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands

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Robert de Jonge Department of Clinical Chemistry, Amsterdam UMC, Vrije Universiteit & University of Amsterdam, Amsterdam, The Netherlands

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A.S. Paul van Trotsenburg Department of Paediatric Endocrinology, Emma Children’s Hospital, Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands

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Anita Boelen Endocrine Laboratory, Department of Clinical Chemistry, Amsterdam Gastroenterology, Endocrinology & Metabolism, Amsterdam UMC, University of Amsterdam, Amsterdam, The Netherlands

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Introduction: Newborn screening (NBS) for congenital hypothyroidism (CH) in the Netherlands consists of thyroxine (T4), thyroid-stimulating hormone (TSH), and T4-binding globulin (TBG) measurements to detect thyroidal CH and central CH (CH-C). CH-C is detected by T4 or a calculated T4/TBG ratio, which serves as an indirect measure of free T4. TSH and TBG are only measured in the lowest 20 and 5% of daily T4 values, respectively. A recent evaluation of the Dutch NBS for CH showed that the T4 and T4/TBG ratio contribute to the detection of CH-C but also lead to a low positive predictive value (PPV). Dried blood spot (DBS) reference intervals (RIs) are currently unknown and may contribute to improvement of our NBS algorithm. Materials and Methods: RIs of T4, TSH, TBG, and the T4/TBG ratio were determined according to Clinical & Laboratory Standards Institute guidelines in heel puncture cards from routine NBS in both sexes and at the common NBS sampling ages. Scatter plots were used to compare the healthy reference population to previously published data of CH-C patients and false positives. Results: Analyses of 1,670 heel puncture cards showed small differences between subgroups and led to the formulation of total sample DBS RIs for T4 (56–118 nmol/L), TSH (<2.6 mIU/L), TBG (116–271 nmol/L), and the T4/TBG ratio (>20). 46% of false-positive referrals based on T4 alone had a TBG below the RI, indicating preventable referral due to partial TBG deficiency. One case of CH-C also had partial TBG deficiency (TBG 59 and T4 12 nmol/L blood). Discussion/Conclusion: Established DBS RIs provided possibilities to improve the PPV of the Dutch CH NBS algorithm. We conclude that by taking partial TBG deficiency into account, approximately half of T4 false-positive referrals may be prevented while maintaining NBS sensitivity at the current level.

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Heleen I Jansen Department of Laboratory Medicine, Endocrine Laboratory, Amsterdam UMC location Vrije Universiteit Amsterdam, Boelelaan, Amsterdam, The Netherlands
Amsterdam Gastroenterology, Endocrinology and Metabolism, Amsterdam, The Netherlands
Department of Laboratory Medicine, Endocrine Laboratory, Amsterdam UMC location University of Amsterdam, Meibergdreef, Amsterdam, The Netherlands

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Marije van Haeringen Department of Laboratory Medicine, Endocrine Laboratory, Amsterdam UMC location University of Amsterdam, Meibergdreef, Amsterdam, The Netherlands
Department of Computer Science, Vrije Universiteit, Boelelaan, Amsterdam, The Netherlands

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Marelle J Bouva Reference Laboratory Neonatal Screening, Center for Health protection, National Institute for Public Health and the Environment, Bilthoven, The Netherlands

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Wendy P J den Elzen Department of Laboratory Medicine, Laboratory Specialized Diagnostics & Research, Amsterdam UMC, University of Amsterdam, Meibergdreef, Amsterdam, The Netherlands
Amsterdam Public Health, Amsterdam, The Netherlands

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Eveline Bruinstroop Amsterdam Gastroenterology, Endocrinology and Metabolism, Amsterdam, The Netherlands
Department of Endocrinology and Metabolism, Amsterdam UMC location University of Amsterdam, Meibergdreef, Amsterdam, The Netherlands

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Catharina P B van der Ploeg TNO - Child Health, Sylviusweg, Leiden, The Netherlands

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A S Paul van Trotsenburg Amsterdam Gastroenterology, Endocrinology and Metabolism, Amsterdam, The Netherlands
Department of Paediatric Endocrinology, Emma Children’s Hospital, Amsterdam UMC, University of Amsterdam, Meibergdreef, Amsterdam, The Netherlands

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Nitash Zwaveling-Soonawala Amsterdam Gastroenterology, Endocrinology and Metabolism, Amsterdam, The Netherlands
Department of Paediatric Endocrinology, Emma Children’s Hospital, Amsterdam UMC, University of Amsterdam, Meibergdreef, Amsterdam, The Netherlands

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Annemieke C Heijboer Department of Laboratory Medicine, Endocrine Laboratory, Amsterdam UMC location Vrije Universiteit Amsterdam, Boelelaan, Amsterdam, The Netherlands
Amsterdam Gastroenterology, Endocrinology and Metabolism, Amsterdam, The Netherlands
Department of Laboratory Medicine, Endocrine Laboratory, Amsterdam UMC location University of Amsterdam, Meibergdreef, Amsterdam, The Netherlands
Amsterdam Reproduction & Development Research Institute, Amsterdam, The Netherlands

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Annet M Bosch Amsterdam Gastroenterology, Endocrinology and Metabolism, Amsterdam, The Netherlands
Department of Pediatrics, Division of Metabolic Disorders, Emma Children’s Hospital, Amsterdam UMC, University of Amsterdam, Meibergdreef, Amsterdam, The Netherlands

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Robert de Jonge Amsterdam Gastroenterology, Endocrinology and Metabolism, Amsterdam, The Netherlands
Department of Laboratory Medicine, Amsterdam UMC, Vrije Universiteit, Boelelaan, Amsterdam, The Netherlands
Department of Laboratory Medicine, Amsterdam UMC, University of Amsterdam, Meibergdreef, Amsterdam, The Netherlands

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Mark Hoogendoorn Department of Computer Science, Vrije Universiteit, Boelelaan, Amsterdam, The Netherlands

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Anita Boelen Amsterdam Gastroenterology, Endocrinology and Metabolism, Amsterdam, The Netherlands
Department of Laboratory Medicine, Endocrine Laboratory, Amsterdam UMC location University of Amsterdam, Meibergdreef, Amsterdam, The Netherlands
Amsterdam Reproduction & Development Research Institute, Amsterdam, The Netherlands

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Objective

Congenital hypothyroidism (CH) is an inborn thyroid hormone (TH) deficiency mostly caused by thyroidal (primary CH) or hypothalamic/pituitary (central CH) disturbances. Most CH newborn screening (NBS) programs are thyroid-stimulating-hormone (TSH) based, thereby only detecting primary CH. The Dutch NBS is based on measuring total thyroxine (T4) from dried blood spots, aiming to detect primary and central CH at the cost of more false-positive referrals (FPRs) (positive predictive value (PPV) of 21% in 2007–2017). An artificial PPV of 26% was yielded when using a machine learning-based model on the adjusted dataset described based on the Dutch CH NBS. Recently, amino acids (AAs) and acylcarnitines (ACs) have been shown to be associated with TH concentration. We therefore aimed to investigate whether AAs and ACs measured during NBS can contribute to better performance of the CH screening in the Netherlands by using a revised machine learning-based model.

Methods

Dutch NBS data between 2007 and 2017 (CH screening results, AAs and ACs) from 1079 FPRs, 515 newborns with primary (431) and central CH (84) and data from 1842 healthy controls were used. A random forest model including these data was developed.

Results

The random forest model with an artificial sensitivity of 100% yielded a PPV of 48% and AUROC of 0.99. Besides T4 and TSH, tyrosine, and succinylacetone were the main parameters contributing to the model’s performance.

Conclusions

The PPV improved significantly (26–48%) by adding several AAs and ACs to our machine learning-based model, suggesting that adding these parameters benefits the current algorithm.

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