Autism Screening at 18 Months of Age: a Comparison of the Q-CHAT and the M-CHAT

Abstract Background: Autism screening is recommended at 18 and 24-month pediatric well visits. The M-CHAT-R screen requires a follow-up interview (M-CHAT-R/F) when positive. M-CHAT-R/F may be less accurate for 18- than 24-month-olds and accuracy for identification prior to two years is not known in samples including children passing screens. Since autism symptoms may emerge gradually, items with ordinal responses, such as Q-CHAT-10, might better capture autism signs than the dichotomous (i.e., yes/no) items in M-CHAT-R. The objective of this study was to determine the accuracy of the M-CHAT-R/F and the Q-CHAT-10 for predicting autism in a sample of children who screen positive or negative at 18 months old.Methods: This is a community pediatrics validation study with screen positive (96) and age and practice-matched screen negative children (314) recruited for diagnostic evaluations completed prior to two years old.Clinical diagnosis of autism based on results of in-person diagnostic autism evaluations by research reliable testers blind to screening results and using the ADOS-2 Toddler module, Mullen Scales of Early Learning (MSEL) per standard guidelines, and ADOS-T algorithm.Results: While the M-CHAT-R/F had higher specificity and PPV compared to M-CHAT-R as expected, performance characteristics, including improved sensitivity with similar PPV, favored Q-CHAT-10 (scoring adjusted to capture the full range of frequency items). Limitations: Many parents declined participation and the sample skewed toward higher educated parents. Results cannot be extended to older ages. Conclusions: The limitations of the M-CHAT-R/F at the 18-month-visit include low sensitivity with minimal balancing benefit of improved PPV from the follow-up interview. The Q-CHAT-10 shows advantages over M-CHAT-R/F including requiring half the number of items and no follow-up interview, yet it did not improve the low PPV at 18 months. Ordinal, rather than dichotomous, scoring of autism screening items appears to be beneficial at this age. The Q-CHAT-10 with adjusted scoring is thus a better alternative to the M-CHAT at the 18-month-visit, providing better detection of children who can be diagnosed at this age even though psychometrics of both approaches still fall below recommended standards, consistent with growing recognition that screening needs to also occur repeatedly beyond this age.