Diagnostic yield of microarrays in individuals with non-syndromic developmental delay and intellectual disability.
Measure head size in every ID/DD assessment—macrocephaly doubles the chance that a microarray will find a genetic cause.
01Research in Context
What this study did
Doctors ordered chromosomal microarrays for the children with non-syndromic ID or DD. All kids came from clinics, not the general public. The team counted how many arrays found a clear genetic cause.
What they found
A definite copy-number variant showed up in a large share of cases. If the child also had macrocephaly, the hit rate jumped even higher. Without big heads, the yield stayed near a large share. With big heads, it leapt to a large share.
How this fits with other research
Cederlund et al. (2014) looked at the preschoolers with ASD in the community. Only a large share had macrocephaly, matching the normal rate. The clash is simple: clinic kids often have more unusual features than kids found in population surveys.
E et al. (199) ran older chromosome tests on 92 PDD cases and found just a large share abnormal. S et al. used modern microarrays and hit a large share. The jump shows the new tool beats the old one.
Estécio et al. (2002) found a large share chromosomal problems in youths with PDD. Their number is close to the a large share here, giving confidence that one in eight to ten kids with unexplained delay has a visible genetic glitch.
Why it matters
When you see a client with ID/DD, measure head circumference. If it is above the 97th percentile, tell the family a microarray has almost double the chance of finding a reason. That single measurement helps you write stronger referrals and sets realistic expectations for genetic counseling.
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02At a glance
03Original abstract
BACKGROUND: Intellectual disability (ID), or developmental delay (DD) when the individual is yet under 5 years of age, is evident before 18 years of age and is characterised by significant limitations in both intellectual functioning and adaptive behaviour. ID/DD may be clinically classified as syndromic or non-syndromic. Genomic copy number variations (CNVs) constitute a well-established aetiological subgroup of ID/DD. Overall diagnostic yield of microarrays is estimated at 10-25% for ID/DD, especially higher when particular clinical features that render the condition syndromic accompany. METHODS: In this study, we aimed to investigate the diagnostic yield of microarrays in the subgroup of individuals with non-syndromic ID/DD (NSID/NSDD). A total of 302 NSID/NSDD individuals who have undergone microarray analysis between October 2013 and April 2020 were included. Accompanying clinical data, including head circumference, delayed developmental areas, seizures and behavioural problems were collected and analysed separately in NSID and NSDD subgroups. RESULTS: The diagnostic yield of microarray analyses in NSID/NSDD was determined as 10.9% in NSID (10.7%) and in NSDD (11.1%). Presence of behavioural and epileptic problems did not contribute to the diagnostic yield. However, in the presence of macrocephaly, the contribution to diagnostic yield was statistically significant particularly in NSDD group. The most common pathogenic CNVs involved chromosomes 16, 15 and X. Lastly, we propose a Xq21.32q22.1 deletion as likely pathogenic in a child with isolated language delay and accompanying seizures. CONCLUSIONS: Particularly in neurodevelopmental diseases, microarrays are useful for establishing the diagnosis and detecting novel susceptibility regions. Future studies would accurately classify the herein presented variants of uncertain significance CNVs as pathogenic or benign.
Journal of intellectual disability research : JIDR, 2021 · doi:10.1111/jir.12892