| Study | Risk of bias | Participants | Intervention | Control | Length of follow-up | Eligibility criteria |
|---|---|---|---|---|---|---|
| Guevera et al.18 | Low | Sample: 2103 Intervention A: 707 Intervention B: 698 Control: 698 Age, mo, mean ± SD Intervention A: 10.5 ± 8.2 Intervention B: 10.5 ± 8.1 Control: 10.4 ± 8.6 Female sex, no. (%) Intervention A: 342 (48.4) Intervention B: 354 (50.9) Control: 351 (50.4) Race/ethnicity data available, no. (%) Intervention A: 553 (78.2) Intervention B: 521 (74.9) Control: 549 (78.9) Loss to follow-up: NR | Caregivers completed the ASQ-II at the 9-, 18- and 30-month well-child visits, and the Modified Checklist for Autism in Toddlers at the 18- and 24-month visits | Caregivers completed the screening tools without the aid of standardized props, either by mail before the well-child visits or at appointment check-in | 18 mo | Age < 30 mo; estimated gestational age > 36 wk; no major congenital anomalies or genetic syndromes; not living in foster care and not currently receiving early intervention services |
| van Agt et al.19 | Unclear | Sample: 55 clusters Intervention: 28 clusters (6485 children) Control: 27 clusters (4955 children) Mean age: NR Female sex, % Overall: 50% Intervention: 50.1% Control: 49.9% Race/ethnicity: NRLoss to follow-up Intervention: 1161 Control: 860 | Structured screening tool (VTO) was completed twice, at 15-18 mo and at 24 mo; the VTO tool consists of a uniform set of questions for parents and test elements for the child | Usual care | 81 mo | Age 15-24 mo during given inclusion period; living in area of intervention physician's or control physician's health care location |
Note: ASQ-II = Ages and Stages Questionnaire II, NR = not reported, SD = standard devision, VTO = VroegTijdige Onderkenning Ontwikkelingsstoornissen Language Screening instrument.