The Child Development Evaluation (or CDE Test) was developed in Mexico as a screening tool for child developmental problems. It yields three possible results: normal, slow development or risk of delay. The modified version was elaborated using the information obtained during the validation study but its properties according to the base population are not known. The objective of this work was to establish diagnostic confirmation of developmental delay in children 16- to 59-months of age previously identified as having risk of delay through the CDE Test in primary care facilities. A population-based cross-sectional study was conducted in one Mexican state. CDE test was administered to 11,455 children 16- to 59-months of age from December/2013 to March/2014. The eligible population represented the 6.2% of the children (n=714) who were identified at risk of delay through the CDE Test. For inclusion in the study, a block randomization stratified by sex and age group was performed. Each participant included in the study had a diagnostic evaluation using the Battelle Development Inventory, 2nd edition. From the 355 participants included with risk of delay, 65.9% were male and 80.2% were from rural areas; 6.5% were false positives (Total Development Quotient ˃90) and 6.8% did not have any domain with delay (Domain Developmental Quotient