Children Who Fail the M-CHAT but Do Not Have ASD: A Comparison of Younger Siblings with Pediatric and Early Intervention Populations

Background: Children who screen positive on the Modified Checklist for Autism in Toddlers (M-CHAT) are at high risk for autism spectrum disorders (ASD) and other developmental disorders. Younger siblings of children with ASD (SIBLING) have higher rates of developmental disorders than the general population and are at risk for ASD and the Broader Autism Phenotype (BAP). Three groups of children were included: SIBLING, pediatrician-referred children (PED), and early intervention-referred children (EI). The EI and SIBLING groups are considered high-risk for ASD and other developmental disorders and thus might have elevated scores on the M-CHAT even without an ASD diagnosis. SIBLING children are more likely to have BAP symptoms and are hypothesized to fail a greater number of ASD-related items than PED and EI. Objectives: To compare M-CHAT scores of SIBLING, PED, and EI children, all of whom failed the M-CHAT and follow-up phone interview but did not have ASD; to determine whether positive screens are more likely to predict ASD and/or other developmental disorders for the high-risk groups; and to determine failed items for the groups. Methods: Sample sizes were: SIBLING = 27, PED = 56, EI = 55. All children failed the M-CHAT and phone interview, were evaluated, and received non-ASD diagnoses. Phone interview data were available for 20 SIBLING, 35 PED, and 34 EI. The M-CHAT has six critical items that best discriminate between ASD and non-ASD. Total and critical scores on the M-CHAT and phone interview, and the proportion of children failing each item, were compared among groups using univariate analyses. Using chi-square analysis, the number in each group with ASD, and the likelihood of having another developmental diagnosis and no diagnosis or typical development, was compared. Results: 67.1% of SIBLING, 43.8% of PED, and 75.6% of EI who failed the M-CHAT had ASD. SIBLING and EI were more likely than PED to have ASD (p<.01). PED was more likely than EI or SIBLING to have another specific disorder, such as global developmental delay or language disorder (p<.001). SIBLING and PED were more likely than EI to have no diagnosis or typical development than EI (p<.001). On the M-CHAT and phone interview, EI failed eye gaze, noise sensitivity, pointing, language comprehension, and staring items significantly more frequently than SIBLING. SIBLING did not fail any items more frequently than EI. On the M-CHAT, PED failed noise sensitivity and staring items more frequently than SIBLING. SIBLING failed directing attention and checking reaction items more often than PED. On the phone interview, PED failed no items more often than SIBLING, but SIBLING failed the directing attention item more frequently than PED. EI had significantly higher total and critical scores on the M-CHAT and phone interview than SIBLING; there were no differences in these scores between SIBLING and PED. Conclusions: EI children likely have more global delays and are more severe as a group, meaning their increased social symptoms may be secondary to their overall delays. SIBLING exhibit social deficits on the M-CHAT more often than PED.