Developmental screening of neurodevelopmental disorders before age 6: a nationwide health screening program

Background: We aimed to investigate the association between developmental screening before 24 months of age and neurodevelopmental disorders (NDDs) at 4-6 years of age. Methods: We included 922,899 newborn born between 2014 and 2016 registered in National Health Insurance Service (NHIS). Developmental screening was administered at 9-12 and 18-24 months old with the Korean Developmental Screening Test for Infants & Children (K-DST). Diagnoses of NDDs was based on the World Health Organization's International Classification of Diseases, Tenth Revision (ICD-10), provided by the NHIS database. Results: Among 637,277 individuals who underwent screening at 9-12 and 18-24 months, Screen-positivity (defined as summed score < -2 standard deviation) for gross motor domain at 9-12 months was significantly associated with the incidence of autism spectrum disorder (aHR, 2.24; 95% CI, 1.80-2.80) and cerebral palsy (aHR, 4.81; 95% CI, 3.62-6.38). Screening positive at language domain at 18-24 months old was associated with autism spectrum disorder (aHR 5.50; 95% CI, 4.31- 7.02) and developmental language disorder (aHR 8.67; 95% CI, 7.27-10.33) at 4-6 years of age. Conclusion: Widespread nationwide implementation of screening programs before 24 months was effective in identifying NDDs at 4-6 years of age. Further strategies integrating with referral and intervention systems should be established. Impact: We investigated the screening effect of nationwide developmental screening program on neurodevelopmental disorders using nationwide data.Gross motor delay during infancy was significant predictor of later neurodevelopmental disorders.Language, cognitive, and social delay before 24 months of age was associated with later autism spectrum disorders and developmental language disorders.Widespread nationwide implementation of screening programs before 24 months was effective in identifying NDDs at 4-6 years of age and should be encouraged.