Establishing paediatric reference intervals for thyroid function tests in Croatian population on the Abbott Architect i2000

Abstract

Introduction Evaluation of thyroid function is often requested and therefore defining paediatric reference intervals (RIs) is of vital importance. Currently, there is a distinct lack of paediatric RIs for thyroid function tests in Croatia. Thus, we established RIs for thyroid stimulating hormone (TSH), total triiodothyronine (TT3), total thyroxine (TT4), free triiodothyronine (FT3) and free thyroxine (FT4) in the Croatian paediatric population. Materials and methods Reference intervals were calculated from 397 apparently healthy children, aged from 2 days to < 19 years. Serum samples were analysed for thyroid function tests on the Abbott Architect i2000. Age- and sex-specific 95% RIs with 90% confidence intervals were established according to Clinical and Laboratory Standards Institute guidelines. To express the magnitude of sex and age variation, standard deviation ratio (SDR) was calculated using two-level nested ANOVA. The criterion for considering partitioning reference values was set to SDR > 0.3. Results All thyroid function tests required age partitioning, confirmed by SDR above 0.3. There was no need for sex partitioning, confirmed by SDR below 0.3. Still, FT3 was partitioned due to visually noticeable sex related difference for the oldest group (12 years to < 19 years). Conclusion This is the first study to establish RIs for thyroid function tests in the Croatian paediatric population. We propose RIs for widely used Abbott platform, thus giving laboratories method- and population-specific paediatric RIs for thyroid function tests that should improve clinical test interpretation.

Laboratory policies and practices for thyroid function tests in Croatia: survey on behalf of Working Group for Laboratory Endocrinology of the Croatian Society of Medical Biochemistry and Laboratory Medicine

“…Additionally, during pregnancy reference interval should be listed according gestation weeks. Unfortunately, most manufacturers do not provide reference intervals for children and pregnant women and many studies are done in order to fill this gap (31)(32)(33). All these issues complicate the interpretation and comparability of laboratory results for TSH and there is an urgent need for standardization of thyroid hormone assays to reduce inter-laboratory variation.…”

Reference intervals for erythrocyte parameters and hemoglobin electrophoresis parameters for young children in Guangxi

“…17,18 The SDR for between-sex SD (SDR sex ) and for between-age SD (SDR age ) was computed as a ratio to residual SD (or between-individual SD). 19 The median and 95% reference intervals for RBC, Hb, MCV, and MCH in all children were presented in Table 1. In judging the need for partitioning RIs of erythrocyte parameters by sex, we calculated the magnitude of between-subgroup variations of RIs as an SDR by twolevel nested ANOVA.…”

“…The need for partitioning RIs by sex and age was judged by standard deviation ratio (SDR) 17,18 . The SDR for between‐sex SD (SDR sex ) and for between‐age SD (SDR age ) was computed as a ratio to residual SD (or between‐individual SD) 19 . Two‐level nested ANOVA was performed to calculate standard deviations (SD) of reference values for sex (SDsex), and age (SDage).…”

Reference intervals for serum TSH concentrations of healthy children from the Central Region of Brazil

“…However, for practical purposes, and with potential therapeutic implications, this evidence was not justified (14). Among children, this evidence was not justified given the variety of TSH RIs across study groups on this subject in this population (15)(16)(17).…”

“…The thyroid analysis consensuses of the Brazilian Society of Endocrinology and Metabolism (Sociedade Brasileira de Endocrinologia e Metabologia -SBEM) are also based on different international studies (8,19). In addition, the heterogeneity in device, determination method and children's age range of available studies hinders the interpretation of different RIs (17,(20)(21)(22)(23). Given the need to standardize a laboratory test to diagnose thyroid dysfunction in the Brazilian pediatric population, the present study was designed to establish the serum TSH concentration RI of healthy children aged from 1 to 10 years of both sexes of a population living in a municipality of the Central Region of Brazil.…”