The targeted high-risk case-finding approach versus universal screening for thyroid dysfunction during pregnancy: thyroid-stimulating hormone (TSH) and/or thyroid peroxidase antibody (TPOAb) test?

Purpose: To compare the effects of different thyroid screening scenarios, using the universal and targeted high-risk case-finding approaches with different diagnostic tests on the prevalence of subclinical hypothyroidism (SCH), thyroid autoimmunity, and pregnancy outcomes after adjustments for the intervention.

Methods: During a secondary analysis of data collected in Tehran Thyroid and Pregnancy Study, a total of 2277 women from the total population, including 1303 high-risk individuals for thyroid dysfunction. The Cochran-Mantel-Haenszel method, adjusted for the intervention, was also used to evaluate the relationships between different screening scenarios [i.e., universal approach using thyroid-stimulating hormone (TSH) and/or thyroid peroxidase antibody (TPOAb) tests and targeted high-risk case-finding approach using TSH and/or TPOAb tests] and pregnancy outcomes (i.e., preterm delivery and NICU admission). The universal approach using both TSH and TPOAb measurements was considered as the reference scenario. We analyzed outcomes of different screening methods in individuals treated with LT4, compared to those individuals who were not treated.

Results: Compared to the universal screening approach with both TSH and TPOAb measurements, the targeted high-risk case-finding approach overlooked approximately 42%, 62%, and 74% of women with elevated TSH (> 4 µlU/mL) when using both TSH and TPOAb tests, TSH alone, and TPO alone, respectively. After adjusting for the missed cases, 2.86% of women with preterm delivery and 2.76% of women with NICU admission were missed when they were screened using the targeted high-risk case-finding approach by measuring both TSH and TPOAb. The percentage of missed cases increased when applying the targeted approach with the TSH test alone, without measuring TPOAb. Overall, 4.16% and 4.02% of women with preterm delivery and NICU admission were overlooked in this scenario, respectively. After adjustments for the intervention, the probability of NICU admission in neonates of mothers, who were screened using the targeted high-risk case-finding approach with TPOAb measurement, was 2.31 folds higher than those screened by the reference scenario.

Conclusion: This study suggests that although the targeted high-risk case-finding approach including both TSH and TPOAb tests, may overlook some women with SCH, it is a reasonable option since it is not associated with a higher risk of adverse pregnancy outcomes.