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<jats:title>BACKGROUND:</jats:title>
<jats:p>This study assessed the concurrent validity of the parent-completed developmental screening measure Ages and Stages Questionnaires, Third Edition (ASQ-3) compared with the Bayley Scales of Infant and Toddler Development, Third Edition (Bayley-III) in children born term, late preterm, or extremely preterm at 8, 18, or 30 months of corrected gestational ages (CGA).</jats:p>
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<jats:title>METHODS:</jats:title>
<jats:p>Data were collected from 306 term and preterm children ages 8, 18, and 30 months’ CGA recruited from an ambulatory well-child clinic in Santiago, Chile. Parents completed the ASQ-3 in their homes, and afterward a trained professional administered the Bayley-III in a clinic setting. On the ASQ-3, the presence of any domain screened &lt;2 SDs below the mean area score was considered a positive screen (indicating failure or delay). A Bayley-III score less than ≤1 SD indicated mild or severe delay.</jats:p>
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<jats:title>RESULTS:</jats:title>
<jats:p>ASQ-3 showed adequate psychometric properties (75% sensitivity and 81% specificity) and modest agreement with the Bayley-III (r = 0.56). Sensitivity, specificity, and correlations between measures improved with testing age and in children who were born extremely preterm.</jats:p>
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<jats:title>CONCLUSIONS:</jats:title>
<jats:p>Considering its psychometric properties, the ASQ-3 can be recommended for routine use in screening low-risk children at 8, 18, and 30 months’ CGA and is advisable to be included in follow-up programs for children with biological risk factors such as those born preterm.</jats:p>
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