Determining the TSH reference range in national newborn screening program for congenital hypothyroidism

Area of Science:

• Endocrinology
• Neonatal Health
• Public Health Screening

Background:

• The Iranian thyroid screening program established a 5 mIU/L threshold for thyroid stimulating hormone (TSH) in 2005.
• Regional disease patterns and ongoing debates necessitate re-evaluating this TSH cutoff point.

Purpose of the Study:

• To propose and evaluate a new TSH cutoff point for congenital hypothyroidism screening in Iran.
• To improve the specificity and reduce false positives in neonatal thyroid screening.

Main Methods:

• Analysis of a database of 127,112 neonates from Markazi Province, Iran (2006-2012).
• Included data from 414 diagnosed hypothyroid neonates and 200 healthy controls.
• Utilized receiver-operator characteristic (ROC) curve analysis and diagnostic values for TSH levels obtained via heel prick tests.

Main Results:

• The existing 5 mIU/L TSH cutoff showed low specificity (10%) and an AUC of 47%.
• A proposed 6.5 mIU/L TSH cutoff demonstrated improved sensitivity (58.9%), specificity (56.5%), and AUC (57%).
• The 6.5 mIU/L cutoff also yielded more favorable likelihood ratios (negative 0.73, positive 1.35).

Conclusions:

• The 5 mIU/L TSH cutoff point exhibits very low specificity, leading to excessive referrals and false positives.
• A TSH cutoff of 6.5 mIU/L is suggested as a more suitable alternative for neonatal congenital hypothyroidism screening in the region.
• Implementing this revised cutoff can enhance the efficiency and accuracy of the screening program.