# Prevalence of Congenital Hypothyroidism and Efficacy of Current Cord Sample Screening in the Presence of Metabolic Screening: A Retrospective Cohort Study

## TL;DR

This study assesses the effectiveness of cord blood screening for congenital hypothyroidism in Saudi Arabia, finding it has high specificity but moderate sensitivity, requiring follow-up serum testing for confirmation.

## Contribution

The study introduces a two-tiered screening approach for congenital hypothyroidism using cord blood and serum testing, improving diagnostic accuracy in a Saudi Arabian population.

## Key findings

- Cord blood screening for CH had 50% sensitivity and 97% specificity, while serum testing had 62.5% sensitivity and 98.6% specificity.
- CH prevalence was 0.8%, consistent with global estimates, with significant risk factors including low birth weight and gestational age.
- Cord blood TSH levels were significantly higher in CH cases compared to non-CH cases.

## Abstract

Background and objectives:Congenital hypothyroidism (CH) is a critical condition that can lead to severe neurodevelopmental impairments if not diagnosed and treated promptly. Early detection through neonatal screening is essential. This study evaluated the efficacy of cord blood free thyroxin 4 (CBFT4) screening for detecting CH in comparison to serum sample testing and newborn metabolic screening (NBS). The aim was to determine the efficacy of current cord blood screening for congenital hypothyroidism in the presence of metabolic screening and to establish the prevalence of CH in a single tertiary center in Saudi Arabia.

Methods: This retrospective cohort study was conducted at Johns Hopkins Aramco Healthcare Center and included all newborns born between January 2021 and December 2023. Both cord blood and heel-prick T4 and thyroid-stimulating hormone (TSH) results were collected from the medical records of 3328 newborns. Diagnostic accuracy parameters were calculated for cord blood and serum findings. Demographic and clinical data were analyzed, including maternal risk factors.

Results: The CH prevalence was 0.8%, which was confirmed by NBS, and there was a higher initial detection rate of 3.4% based on cord blood screening. The average level of cord blood total thyroxin 4 (CBTT4) was 6.48 ± 0.78 µg/dL, and the cord blood TSH was 5.9 ± 6.4 µIU/mL. Serum FT4 levels were 1.3 ± 0.5 ng/dL, and serum TSH levels were 8.7 ± 24.5 µIU/mL. The sensitivity and specificity of cord blood diagnosis were 50% and 97%, respectively, while serum sample diagnosis had a sensitivity of 62.5% and a specificity of 98.6%. Significant associations were found between lower birth weight (2.146 ± 0.771 kg vs. 2.801 ± 0.662 kg; p = 0.006), lower gestational age (35 ± 3 weeks vs. 37 ± 3 weeks; p = 0.008), and CH. Cord blood TSH levels were significantly higher in CH cases (32.9 ± 55.2 µIU/mL vs. 5.7 ± 3.7 µIU/mL; p < 0.001).

Conclusion: Cord blood screening for congenital hypothyroidism demonstrates moderate sensitivity and high specificity, indicating that it is reliable for ruling out the condition but necessitates confirmatory serum testing due to the risk of false positives. The prevalence of CH in this cohort aligns with global estimates. Lower birth weight, lower gestational age, and maternal thyroid disease are significant risk factors for CH. A two-tiered screening approach with follow-up serum testing is recommended to improve diagnostic accuracy and ensure timely intervention.