Free T4 Age-Specific Reference Intervals from Birth to the 10^th Decade of Life Using Direct Dialysis

Area of Science:

• Endocrinology
• Clinical Chemistry
• Laboratory Medicine

Background:

• Current free thyroxine (FT4) reference intervals (RIs) often fail to account for age-specific variations.
• This limitation impacts accurate diagnosis and management, especially in neonates and older adults.
• Lack of age-specific interpretive criteria hinders precise clinical decision-making.

Purpose of the Study:

• To establish comprehensive, age-based free thyroxine (FT4) reference intervals (RIs) from birth to 100 years.
• To provide clinicians with precise contextual data for FT4 result interpretation across the entire lifespan.
• To improve the accuracy of diagnosing and managing thyroid-related conditions.

Main Methods:

• Utilized multi-modal decomposition (MMD) analysis on over 1.8 million de-identified retrospective FT4 results.
• Analyzed specimens from a commercial reference laboratory covering ages 0 to 100 years.
• Validated the derived RIs using a separate, independent dataset.

Main Results:

• Developed 14 distinct age-specific FT4 reference intervals (RIs).
• Observed broadest FT4 intervals at birth, narrowing through childhood towards adult ranges.
• Identified a slight increase in the upper reference limit (URL) for older adults.

Conclusions:

• Validated FT4 RIs offer crucial interpretive criteria for all age groups.
• Age-specific RIs for neonatal, pediatric, and adult populations enhance diagnostic accuracy.
• Enables more precise classification of abnormal FT4 results by providing appropriate clinical context.