First Estimation of Reference Intervals for Thyroid-Stimulating Hormone and Thyroid Hormones in Slovenian Population

Adrijana Oblak,Ajda Biček,Edvard Pirnat,Simona Gaberšček,Katja Zaletel

doi:10.17344/acsi.2020.5922

Abstract

For thyroid function estimation and clinical decision making, use of appropriate reference intervals for thyroid-stimulating hormone (TSH), free thyroxine (fT4) and free triiodothyronine (fT3) is crucial. For each laboratory, establishment of own reference intervals is advised. For the first Slovenian estimation of reference intervals for thyroid hormones a large group of 1722 healthy individuals without thyroid disease was established retrospectively. Hormone analyses were performed on automated analyser Advia Centaur XP Immunoassay System (Siemens Healthineers), which reference intervals for TSH, fT4 and fT3 were 0.55-4.78 mIU/L, 11.5-22.7 pmol/L, and 3.5-6.5 pmol/L, respectively. Statistical analysis followed non-parametric percentile method. Our laboratory reference intervals for TSH, fT4 and fT3 are mostly narrower than intervals given by manufacturer. Median value, lower and upper limit for TSH, fT4 and fT3 were 1.98 (0.59-4.23) mIU/L, 14.5 (11.3-18.8) pmol/L and 4.82 (3.79-6.05) pmol/L, respectively. Most likely, an inclusion of a high number of healthy individuals without thyroid disease was a reason for such results.

Highlights

Biochemical parameters obtained from blood sampling are an important part of clinical decision-making
Hormone analyses were performed on automated analyser Advia Centaur XP Immunoassay System (Siemens Healthineers), which reference intervals for thyroid-stimulating hormone (TSH), fT4 and fT3 were 0.55–4.78 mIU/L, 11.5–22.7 pmol/L, and 3.5–6.5 pmol/L, respectively
Studies have shown that the time of sample collection has an impact on serum TSH value and should be standardized to minimize the impact of false TSH values on clinical decisions especially in subclinical hypothyroidism, which is defined as elevated TSH, and normal free thyroxine and free triiodothyronine values.[6]

Summary

Introduction

Biochemical parameters obtained from blood sampling are an important part of clinical decision-making. A path from ordering a test by a clinician to the value of an analyte in blood is long and is facing several important and critical steps which can influence the end result and, a clinical decision. Important part of this process is preanalytics which combines different aspects – from biological variability to sample collection and sample handling prior to analysis.[1] Preanalytics is a source of majority of errors and should be carefully executed.[2] The primary goal of every medical examination is to cause no harm to a patient.

Objectives

Results

Conclusion