Diagnostic yield of chromosomal microarray analysis in an autism primary care practice: which guidelines to implement?

Doctors ran chromosomal microarray analysis (CMA) on autistic patients in a primary-care clinic. They wanted to know if CMA finds more problems than older tests like karyotype or Fragile X.

The team looked at every test result and counted how many showed clear, clinically useful changes.

CMA gave an abnormal result in 24% of the patients. Eight of those results were clearly important for care.

Older tests found far less. CMA won.

Al-Mamari et al. (2015) repeated the same idea in families with lots of cousin marriages and got 27%. The two studies back each other up: about one in four autistic kids shows a useful CNV.

Older papers using karyotype told a different story. Konstantareas et al. (1999) and Gaily et al. (1998) each found only 3.2% abnormal. The gap looks like a contradiction, but it is not. Karyotype misses small deletions and duplications that CMA can see. G et al. simply used a stronger microscope.

Pitetti et al. (2007) added subtelomere FISH and found zero extra cases, showing that more old-tech tests do not help. Duerden et al. (2012) therefore replaces the low-yield karyotype-plus-add-ons approach with a single high-yield CMA step.

If you refer an autistic client for genetic testing, ask the physician to order CMA first. It gives families an answer four times more often than the old standard. A clear genetic finding can guide medical follow-up, inform prognosis, and give caregivers a concrete reason for the diagnosis.