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. 2021 Apr;10(2):140-149.
doi: 10.1159/000507018. Epub 2020 May 5.

Variability of Thyroid Measurements from Ultrasound and Laboratory in a Repeated Measurements Study

Till Ittermann  1 , Adrian Richter  1   2 , Martin Junge  1 , Matthias Nauck  3 , Astrid Petersmann  3   4 , Clemens Jürgens  1 , Harald Below  5 , Carsten Oliver Schmidt  1 , Henry Völzke  1
Affiliations

Variability of Thyroid Measurements from Ultrasound and Laboratory in a Repeated Measurements Study

Till Ittermann et al. Eur Thyroid J. 2021 Apr.

Abstract

Background: Variability of measurements in medical research can be due to different sources. Quantification of measurement errors facilitates probabilistic sensitivity analyses in future research to minimize potential bias in epidemiological studies. We aimed to investigate the variation of thyroid-related outcomes derived from ultrasound (US) and laboratory analyses in a repeated measurements study.

Subjects and methods: Twenty-five volunteers (13 females, 12 males) aged 22-70 years were examined once a month over 1 year. US measurements included thyroid volume, goiter, and thyroid nodules. Laboratory measurements included urinary iodine concentrations and serum levels of thyroid-stimulating hormone (TSH), free triiodothyronine (fT3), free thyroxine (fT4), and thyroglobulin. Variations in continuous thyroid markers were assessed as coefficient of variation (CV) defined as mean of the individual CVs with bootstrapped confidence intervals and as intraclass correlation coefficients (ICCs). Variations in dichotomous thyroid markers were assessed by Cohen's kappa.

Results: CV was highest for urinary iodine concentrations (56.9%), followed by TSH (27.2%), thyroglobulin (18.2%), thyroid volume (10.5%), fT3 (8.1%), and fT4 (6.3%). The ICC was lowest for urinary iodine concentrations (0.42), followed by fT3 (0.55), TSH (0.64), fT4 (0.72), thyroid volume (0.87), and thyroglobulin (0.90). Cohen's kappa values for the presence of goiter or thyroid nodules were 0.64 and 0.70, respectively.

Conclusion: Our study provides measures of variation for thyroid outcomes, which can be used for probabilistic sensitivity analyses of epidemiological data. The low intraindividual variation of serum thyroglobulin in comparison to urinary iodine concentrations emphasizes the potential of thyroglobulin as marker for the iodine status of populations.

Keywords: Iodine; Measurement error; Thyroglobulin; Thyroid; Thyroid imaging; Thyroid-stimulating hormone; Variability.

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Conflict of interest statement

The authors declare that they have no conflict of interest.

Figures

Fig. 1
Fig. 1
Visit-specific medians (25th and 75th percentile) for continuous thyroid biomarkers. fT3, free triiodothyronine; fT4, free thyroxine; TSH, thyroid-stimulating hormone.
Fig. 2
Fig. 2
Individual CVs plotted against the individual means. CV, coefficient of variation; fT3, free triiodothyronine; fT4, free thyroxine; TSH, thyroid-stimulating hormone.
Fig. 3
Fig. 3
Individual variation of thyroid biomarkers. fT3, free triiodothyronine; fT4, free thyroxine; TSH, thyroid-stimulating hormone.
Fig. 4
Fig. 4
Diurnal variation of serum TSH levels. TSH, thyroid-stimulating hormone.
See this image and copyright information in PMC

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