Dimensional Scoring of Parent Report Screens for Autism Improves Accuracy at the 18-Month Pediatric Visit
Screening for Autism is recommended by the American Academy of Pediatrics (AAP) at both 18 and 24-month check-up visits. The Modified Checklist for Autism in Toddlers-Revised (M-CHAT-R), which is a recommended and the most commonly used screening measure, has been shown to require a follow-up interview (M-CHAT-R/F) to reduce false positives (Kleinman, et. al., 2008); however, this interview is an implementation challenge. Additionally, the M-CHAT-R may be less accurate for 18-month olds than 24-month olds (Pandey, et. al., 2008; Sturner, et. al., 2017a). Since autism symptoms may emerge gradually in toddlers (Ozonoff, 2008) and most M-CHAT item failures in younger toddlers are for later emerging milestones (Sturner, et. al., 2017b), we reasoned that items allowing dimensional responses (e.g., “how much”), such as the Parent Observation of Social Interaction (POSI; Smith,.et. al., (2013)) and the Quantitative Checklist for Autism in Toddlers (Q-CHAT-10; Allison, et. al., 2012), might better capture signs of autism than the yes/no items used in the M-CHAT-R. Although the POSI and Q-CHAT comprise dimensional responses, they still use dichotomous scoring systems.
To compare the predictive utility at 16-20 months of the M-CHAT-R/F, which uses a yes/no response format, with the predictive utility of POSI and Q-CHAT-10, two screens which use dimensional response items.
Parents of 16-20 month olds completed the M-CHAT-R and the Q-CHAT-10 before 18-month pediatric visits via an online system (CHADIS). Children with positive screens (96) on either the M-CHAT-R/F or Q-CHAT-10 were recruited along with age and practice-matched controls (314). Parents subsequently completed the POSI. Children were assessed with the Mullen Scales of Early Learning (MSEL; Mullen, 1995)) and Autism Diagnostic Observation Schedule - Toddler Version (ADOS-T; Lord, et. al. 2000). The ADOS-T and clinical judgement were used to determine whether a child met sufficient criteria for autism to be considered a positive. Comparisons of estimated ROCs were conducted between the tools using two one-sided tests of equivalence (TOST).
Dimensional scoring improved the specificity of Q-CHAT-10 with less benefit to the POSI. Although separately similar to M-CHAT-R, a combination of the QCHAT-10 and POSI that used dimensional scoring (D/Q-CHAT-10 + D/POSI) had better sensitivity than the currently recommended M-CHAT-R/F and better specificity compared to M-CHAT-R with comparable PPV and without requiring a follow-up interview.
Autism screening measures for young toddlers that use dimensional response items may have advantages over the categorical yes/no item format. This combined dimensionally scored D/Q-CHAT-10+ D/POSI is not only more accurate than a widely used categorical screen, but also more efficient, as it uses a similar number of questions (17 for Q-CHAT-10+D/POSI and 20 for M-CHAT-R) but does not require the follow-up interview of the M-CHAT-R. However, none of these screens have improved the known problem of low PPV at this visit age.