Estudos Psicométricos da versão Brasileira do Modified Checklist for Autism in Toddlers (MCHAT)

Abstract

Autism spectrum disorder (ASD) is part of a group of neurodevelopmental disorders whose symptoms begin early, with persistent deficiencies in social communication and social interaction, in addition to repetitive and stereotypical behavior and a restriction in interests and activities. Early diagnosis and intervention are associated with a better prognosis in both cognitive and adaptive functioning and in reducing the severity of the central symptoms of ASD, however, in Brazil there is a lack of instruments to track early signs of ASD, which leads to many children to be diagnosed late. The present study aimed to evaluate the psychometric properties of the Modified Checklist for Autism in Toddlers (M-CHAT) in a children population in Montes Claros, Minas Gerais. This is a methodological study whose sample consisted in 1204 children aged up to 36 months, divided in two groups: 88 children with ASD (group 1) and 1116 children without ASD (group 2). This research used a version of of M-CHAT translated into Brazilian Portuguese. This instrument consists of 23 items with "yes" or "no" answers, indicating the presence or absence of behaviors known as early signs of ASD, six of which are considered critical for ASD. Two criteria were used to identify children "at risk for ASD": any child who failed (to score) on at least two of the six critical items or on at least three of the 23 MCHAT items. The psychometric properties of M-CHAT analyzed were: reliability (internal consistency and reproducibility), sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and discriminant validity. Internal consistency was evaluated using the Kuder-Richardson coefficient, (KR21), and reproducibility using the Kappa coefficient and Intraclass Correlation (ICC). Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) were estimated, with respective 95% confidence intervals, and the Receiver Operating Characteristic (ROC) curve was also constructed. To analyze discriminant validity, the two groups were compared with regards the proportion of failures for each M-CHAT item using the Chi-square test or Fisher's Exact test. The number of failures was also compared according to sex, age-group and participant group (groups 1 and 2) using the Mann-Whitney test. For the two criteria evaluated (2 of the 6 critical itens e 3 of 23), the M-CHAT presented high internal consistency (0.78 and 0.86), satisfactory reproducibility (Kappa from 0.60 to 0.79 and ICC = 0.87 and 0.89), high sensitivity (0.807 and 0.932), specificity (0.927 and 0.706) and NPV (0.984 and 0.992), however the PPV estimates (0.467 and 0.250) were not satisfactory. Regarding discriminant validity, it was observed that the proportion of failures was significantly higher in the group of children with ASD in all items of the instrument. It was also observed that the number of failures was higher among male children, from the 2536-month age range and in the group with ASD. The Brazilian version of M-CHAT has adequate psychometric properties at the level of reliability, specificity, NPV and discriminant validity, which makes it viable to be applied in research in clinical contexts. However, we must also stress the importance of using the interview suggested by the original authors of the M-CHAT, in conjunction with this instrument, in order to reduce the number of false positive cases.