Screening for autism in older and younger toddlers with the Modified Checklist for Autism in Toddlers.
One M-CHAT at 18 months is not enough for low-risk toddlers—rescreen at 24 months or refer for full assessment.
01Research in Context
What this study did
Pandey et al. (2008) asked whether the M-CHAT catches autism better at 18 months or 24 months. They screened low-risk toddlers at two age bands: 16-23 months and 24-30 months.
Every child who failed the screen was tracked until a final diagnosis was made. The team then compared how often each age group truly had autism.
What they found
The M-CHAT was more accurate at 24-30 months than at 16-23 months. Screening at 18 months missed more autism cases in low-risk toddlers.
Most children who failed the screen did have some developmental delay, even if it was not autism.
How this fits with other research
Hampton et al. (2015) pooled data from five parent screeners and found that social-interaction items drive accuracy. Their meta-analysis includes the 2008 data, showing the M-CHAT works when key items are present.
Tsai et al. (2019) later tested the revised M-CHAT-R/F in Taiwanese toddlers and reported strong numbers. Their positive results extend the 2008 work by showing the newer version performs well across cultures.
van den Broek et al. (2006) had already warned that the M-CHAT can miss higher-functioning children. Pandey et al. (2008) echo this caution and add the age twist: younger toddlers are even harder to catch.
Why it matters
If you screen a low-risk 18-month-old who fails the M-CHAT, do not relax after one pass. Schedule a second screen around 24 months or move straight to a full autism evaluation. This double-check cuts false negatives and aligns with later studies that found better accuracy at older ages.
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02At a glance
03Original abstract
The Modified Checklist for Autism in Toddlers (M-CHAT) was used to screen younger (16-23 months) versus older (24-30 months) high- and low-risk toddlers. Refusal rates for follow-up interview showed no group differences, but parents of younger/low-risk children were more likely to refuse evaluation than parents of high-risk children. PPP for an ASD diagnosis was: younger/high-risk 0.79, older/high-risk 0.74, younger/low-risk 0.28, and older/low-risk 0.61, with PPP differing by age within the low-risk group. Most of the children in all groups, however, were diagnosed with a developmental disorder. Symptom severity generally did not differ among groups. Cognitive and adaptive measures showed minimal group differences. Therefore, older and younger toddlers had similar symptomatology and developmental delays; PPP for ASD is better at 24 than 18 months for low-risk children; however, these children are still highly likely to show a developmental disorder. Clinical decision making should balance early identification against the lower specificity of M-CHAT screening for the younger/low-risk group.
Autism : the international journal of research and practice, 2008 · doi:10.1177/1362361308094503