Types and Results of Genetic Testing
In March 2010, WebMD announced a study demonstrating that a new type of genetic test is superior to two older tests. Prior to the new test, known as “chromosomal microarray analysis” (CMA), two other tests had routinely been part of a child’s health screening.  These other two tests, operating at the microscopic level, are G-banded karyotype testing and fragile X testing; findings about the effectiveness of these two tests after compiling results from over 800 patients were:
G-banded karyotype testing: standard genetic test yielded abnormal findings in about 2 percent of patients.
Fragile X testing: found abnormal results in about .5 percent of patients.
The new test, CMA, operates at the molecular level. Its results were significantly higher than those from either of the other two tests; finding abnormalities in about 18 percent of the patients. Out of the 18 percent, about 7 percent revealed “possible or known genetic disorders.”  The doctors and researchers involved in the compilation and review of statistics agreed that the new CMA test should be a required part of every screening, due to its higher rate of detecting abnormalities related to genetic disorders. Further, autism expert and director of the MIND Institute at University of California, Davis, Randi Hagerman, MD, stated that for anyone with autism, the CMA test "is the No. 1 test to yield an abnormal result." 
The primary benefit of genetic testing, particularly the CMA test, is its ability to detect genetic disorders related to autism earlier than through other types of screening. Earlier detection yields earlier intervention and treatment. This in turn can potentially improve the lives of autistic children and their families. Another benefit of genetic testing is assisting parents with determining whether they want to take the risk of having additional children who may also have autism. 
Genetic testing has its limitations. Bai-Lin Wu, PhD, the medical director of the genetics diagnostic laboratory at Children's Hospital, Boston, stated that genetics only account for about 15 percent of autism cases; of that number, the CMA tests only verify about 7 percent. Other limitations of genetic testing include the fact that the testing is cost-prohibitive to families, typically over $1,000, and insurance doesn’t cover it. In addition, the CMA test is not conclusive as a specific test for autism alone and requires more research studies to confirm its relevance and reliability for autism diagnoses.