Table 1 –

Four item pool domains and subsequent sub-domain within each. Legacy measures listed represent example assessment tools and developmental checklists used to inform items.

Item pool domains and subdomains:	Example legacy measures used to inform item content for each domain:	Example items within each domain:
• Physical Functioning  ◦ Gross motor  ◦ Fine motor	• Survey of Well-being of Young Children Developmental Milestones [48] • PROMIS Parent Proxy Item Bank v2.0 — Upper Extremity [49] • Burn Outcomes Questionnaireo0–4 [14] • Child Development Inventory [50] • PROMIS Parent Proxy Mobility [51] • Ages and Stages Questionnaire-3 (ASQ) [52] • Battelle Developmental Inventory- Second Edition (BDI-2) [53] • CDC Milestones Checklist [1] • Bayley Scales of Infant Development [54]	• Kick a balla • Put on his/her socks without helpa
• Psychological Functioning  ◦ Internalizing   - Depression   - Withdrawal   - Anxiety   - Separation Distress  • Externalizing   - Aggression   - Defiance  • Dysregulation   - Negative emotionality   - Sleep behaviors   - Eating behaviors  • Trauma  • Toileting	• Burn Outcomes Questionnaire0–4 [14] • Infant and Toddler Social Emotional Assessment [55] • NIH Toolbox — Fear — Over Anxious (Ages 3—7) Parent Report [56] • Brief Infant and Toddler Social Emotional Assessment [57] • Survey ofWell-being ofYoung Children Pediatric Symptom Checklist [48] • Achenbach Child Behavior Checklist [58] • Ages and Stages Questionnaire: Social-Emotional (ASQ) [59] • PROMIS Parent Proxy Item Bank v2.0 — Anxiety [60] • PROMIS Parent Proxy Item Bank v2.0 — Depressive Symptoms [60] • PROMIS Pediatric Item Bank v1.0 — Positive Affect [61] • Temperament and Atypical Behavior Scale (TABS) [62] • KiddyKINDL parent questionnaire 4—6 years [63] • Pediatric Symptom Checklist (PSC) — 35 [64] • PROMIS Parent Proxy — Physical Stress Experiences [65]	• Seemed unresponsive to affectionb • Seemed withdrawnb • Needed to be told over and over things were okayb • Cried or hung on to me when I tried to leaveb • Was aggressiveb • Destroyed things belonging to othersb • Was whiny or fussy when he/she was not tiredb • Had trouble falling asleep at nightb • Refused to eatb • Avoided doing this that reminded him/her of the injuryb • Used the toilet on his/her ownb
• Social Functioning  ◦ Connecting with family/peers  ◦ Friendships  ◦ Play	• NIH Toolbox Fixed Form v2.0 — Companionship — Positive Peer Interactions (Ages 3—12) Parent Report [56] • Infant and Toddler Social Emotional Assessment [55] • Burn Outcomes Questionnaire0–4 [14] • Survey of Well-being of Young Children [48] • Brief Infant and Toddler Social Emotional Assessment [57] • Ages and Stages Questionnaire: Social-Emotional (ASQ) [59] • NIH Toolbox Fixed Form v2.0 — Companionship — Social Withdrawal (Ages 3—12) Parent Report [56] • NIH Toolbox Fixed Form v2.0 — Social Distress — Peer Rejection (Ages 3—12) Parent Report [56] • PROMIS Parent Proxy — Peer Relationships [66]	• Got along with other children of the same sexb • Had at least one favorite friend (a child)b • Initiated familiar play routinesb
• Communication and Language Development  ◦ Receiving language  ◦ Producing language	• American Speech-Language Hearing Developmental Guide [67] • Burn Outcomes Questionnaire0–4 [14] • Survey of Well-being of Young Children [48] CDC Milestones Checklist [1]	• Could follow two-part instructions- like “Get the spoon and put it on the table”a • Used 4—5 word sentencesb

^aItem aims to assess ability; response options: unable to do, with much difficulty, with some difficulty, with little difficulty, with no difficulty.

^bItem aims to assess frequency of behavior: response options: never, rarely, sometimes, often, always.