Boston Children’s Hospital researchers have developed a prototype blood test for autism, and preliminary results published Wednesday suggest it could one day be used to help diagnose the disorder when children are very young and respond best to treatment.

The test, which measures the activity of dozens of genes, was able in one group to predict with about 70 percent accuracy whether a boy was at risk for autism or not. Outside researchers cautioned that the work has limitations and that the blood test needs much more study before it is clear whether it could be a useful tool for doctors and parents.