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

Area of Science:

• Endocrinology
• Clinical Chemistry
• Pediatrics

Background:

• Accurate pediatric reference intervals (RIs) for thyroid function are vital for clinical evaluation.
• A significant gap exists in established pediatric RIs for thyroid tests in Croatia.
• This study addresses the need for population-specific RIs for thyroid stimulating hormone (TSH), total triiodothyronine (TT3), total thyroxine (TT4), free triiodothyronine (FT3), and free thyroxine (FT4).

Purpose of the Study:

• To establish method- and population-specific pediatric reference intervals for key thyroid function tests in Croatia.
• To provide Croatian laboratories with reliable data for interpreting thyroid function tests in children.
• To enhance the accuracy of diagnosing thyroid disorders in the pediatric population.

Main Methods:

• Analysis of serum samples from 397 healthy children aged 2 days to 19 years.
• Thyroid function tests performed on the Abbott Architect i2000 platform.
• Calculation of age- and sex-specific 95% RIs with 90% confidence intervals following CLSI guidelines, using standard deviation ratio (SDR) for partitioning criteria.

Main Results:

• All tested thyroid function tests required age-specific partitioning, with SDRs exceeding 0.3.
• Sex-specific partitioning was not generally required, as SDRs were below 0.3.
• Free triiodothyronine (FT3) showed a notable sex-related difference in the oldest age group (12–19 years) and was thus partitioned.

Conclusions:

• This research presents the first established reference intervals for thyroid function tests in the Croatian pediatric population.
• The proposed RIs are specific to the widely used Abbott platform.
• Implementation of these population- and method-specific RIs is expected to improve the clinical interpretation of thyroid function tests in Croatian children.