Consistency between research and clinical diagnoses of autism among boys and girls with fragile X syndrome.
Half of kids with fragile X meet research autism criteria, yet clinics label only a quarter—girls are the main miss.
01Research in Context
What this study did
The team looked at 120 boys and girls with fragile X syndrome. They compared two labels: the autism diagnosis each child already had from community doctors, and the autism label given by a research team using gold-standard tests.
Kids took the ADOS and ADI-R. If they scored above the cutoff on both, the study called them "research-positive" for ASD. The scientists then counted how many research-positive children were missed in everyday clinics.
What they found
Half of the fragile X kids met research criteria for autism, but only one quarter had a clinic chart saying ASD. In plain numbers, 25 out of 60 research-positive children had no clinical diagnosis.
Girls were missed more often than boys. The gap shows the system is not catching autism in females with fragile X.
How this fits with other research
Hodge et al. (2025) saw the same late-find pattern in the general autism clinic: girls are evaluated six months later than boys because their symptoms look milder. Together, the two studies say "look twice at girls."
Bassett-Gunter et al. (2017) seems to disagree. They tested 679 autistic kids and found boys and girls scored almost the same on symptom tests. The clash disappears when you see the populations: fragile X girls have a known protective effect that lowers clinical signs, while L’s sample was already diagnosed and thus more obvious.
Ivy et al. (2017) adds that the ADOS itself is not biased; it measures autism the same way in both sexes. So the tool is fine—our eyes are the problem.
Why it matters
If you work with fragile X, add an autism screen even when parents don’t raise the question. Use the ADOS plus parent interview, and watch for subtle social passivity in girls. Catching ASD early lets you start social and communication interventions during the critical window, improving long-term outcomes for an often-overlooked group.
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02At a glance
03Original abstract
BACKGROUND: Prior research suggests that 60-74% of males and 16-45% of females with fragile X syndrome (FXS) meet criteria for autism spectrum disorder (ASD) in research settings. However, relatively little is known about the rates of clinical diagnoses in FXS and whether such diagnoses are consistent with those performed in a research setting using gold standard diagnostic tools. METHOD: This study explored whether boys and girls with FXS met criteria for ASD in a research setting using the Autism Diagnostic Observation Schedule (ADOS) and the Autism Diagnostic Interview-Revised (ADI-R), and then compared these data with the frequency of parent-reported clinical diagnoses. We also examined child and family characteristics as potential diagnostic predictors across settings. Participants included 35 females and 51 males with FXS (mean age: 10 years), who were from Eastern and Midwestern regions of the USA. RESULTS: About half of the children met criteria for ASD on either the ADOS or ADI-R, with ASD occurring three times more frequently in males than females (∼75% vs. ∼25%). In contrast, ∼25% of participants of both genders had received a clinical diagnosis of ASD. While cognitive and language skills predicted diagnostic outcome on the ADOS and ADI-R, these skills did not predict clinical diagnoses. Executive functions predicted clinical diagnoses, but not diagnoses per the ADOS or ADI-R. CONCLUSIONS: ASD in FXS may be under-diagnosed in clinical/educational settings, which raises questions regarding access to ASD-related services.
Journal of intellectual disability research : JIDR, 2014 · doi:10.1111/jir.12121