Neonatal plasma TSH--estimated upper reference intervals for diagnosis and follow up of congenital hypothyroidism

Area of Science:

• Endocrinology
• Paediatric diagnostics
• Clinical chemistry

Background:

• Accurate plasma thyroid-stimulating hormone (TSH) reference intervals are vital for diagnosing and managing congenital hypothyroidism in infants.
• Establishing reliable reference intervals is challenging due to difficulties in obtaining samples from healthy paediatric populations.

Purpose of the Study:

• To estimate method-dependent plasma TSH upper-reference intervals for paediatric use.
• To overcome limitations in obtaining healthy paediatric plasma samples for TSH analysis.

Main Methods:

• Determined the blood spot TSH upper-reference interval from a large newborn screening dataset (N = 10,697).
• Derived method-dependent conversion factors from paired blood spot and plasma TSH measurements.
• Calculated plasma TSH upper-reference intervals for five different TSH assay methods.

Main Results:

• The blood spot TSH upper-reference interval was established at 3.04 mU/L (97.5th centile).
• Estimated plasma TSH upper-reference intervals varied by assay method, ranging from 6.3 to 8.3 mU/L.
• Specific upper reference intervals were provided for Siemens Centaur, Abbott Architect, Roche Elecsys E170, Siemens Immulite 2000, and Beckman Access HYPERsensitive TSH assays.

Conclusions:

• The estimated method-dependent plasma TSH upper reference intervals are practical tools for clinicians.
• These intervals will assist in diagnosing and monitoring infants with elevated blood spot TSH concentrations identified through newborn screening.