Chromosomal microarray analysis (CMA), which screens the entire genome for tiny blips in the sequence, should be the first genetic test performed when diagnosing autism, a consortium of clinical geneticists recommends in the 14 May American Journal of Human Genetics.The recommendation comes on the heels of an April Pediatrics study that found the test is three times more effective at spotting autism variants than are standard clinical methods.Most clinics rely either on karyotyping — which involves looking at chromosomes under a microscope for gross irregularities — or testing for fragile X syndrome, the most common inherited form of autism, by analyzing the FMR1 gene on the X chromosome.Because these measures only catch the most obvious genetic problems, however, they produce positive results in only about five percent of children tested.CMA uses gene chips to pick up more subtle genetic mutations across the genome, making it more likely that abnormalities will be found, experts say.Read more at...SFARI, May 2010.