Esin, Ibrahim SelcukDemirdogen, Esen YildirimAkinci, Mehmet AkifTuran, BahadirUruk, Gulsum Tugba KorkmazUcuz, Ilknur IbiliDursun, Onur Burak2026-04-042026-04-0420252076-3425https://doi.org/10.3390/brainsci16010062https://hdl.handle.net/11616/108642Objective: This study aimed to provide a reliable estimate of early childhood autism spectrum disorder (ASD) prevalence in T & uuml;rkiye and to examine diagnostic stability and developmental trajectories through a ten-year longitudinal follow-up incorporating systematic early screening, structured parent-child observations, and repeated diagnostic assessments. Methods: A total of 1981 children aged 18-48 months were screened using the M-CHAT-R/F. Children who screened positive underwent an initial clinical assessment, including a family interview and structured parent-child observation. Those identified as at risk were referred for DSM-5-TR-based diagnostic evaluation by expert clinicians. Children diagnosed with ASD or classified as at risk were enrolled in a structured ten-year follow-up program. Results: Of the 1981 screened children, 27 (1.4%) were identified as at risk. Nine children (33.3% of at-risk; 0.45% of the total sample) received an ASD diagnosis following comprehensive evaluation. All retained their diagnosis during the 18-month follow-up. By the tenth year, two additional children from the at-risk group were diagnosed, bringing the total number of ASD cases to 11. Conclusions: These findings demonstrate that structured, multi-stage screening and diagnostic procedures are feasible and effective for early ASD identification in T & uuml;rkiye. High diagnostic stability supports the reliability of early clinician-led assessments, while later-emerging cases highlight the importance of long-term monitoring of at-risk children.eninfo:eu-repo/semantics/openAccessautism spectrum disorderprevalencediagnostic stabilitylongitudinal studyArticle1614159478310.3390/brainsci160100622-s2.0-105028592906Q2WOS:001670796600001Q30000-0002-2457-5832