A brainwave test that measures the amount of time the brain responds to sights and sounds might be able to identify how severe a patient's autism is and also help diagnose the condition sooner, according to a paper published yesterday in the online edition of the Journal of Autism and Developmental Disabilities.

One in 68 children have been diagnosed with autism spectrum disorder (ASD), according to the U.S. Centers for Disease Control and Prevention. Depending on the severity of the condition, the symptoms can vary from mild social and communication problems to significant cognitive impairments.

Right now, there isn't a medical test to diagnose autism. Instead, physicians evaluate a patient's behavioral characteristics and symptoms.

"These assessments can be highly subjective and require a tremendous amount of clinical expertise," Dr. Sophie Molholm, leader of the study and associate professor at Albert Einstein College of Medicine of Yeshiva University, said in a statement. "We clearly need a more objective way to diagnose and classify this disorder."

Brainwave electroencephalogram (EEG) recordings might be the objective test physicians need. A study that Dr. Molholm conducted two years ago found that EEG might be able to show how severely ASD patients are affected.

For this new study, the researchers at the university set out to determine if sensory processing varies depending on the severity of autism. They pooled together 43 ASD patients between six and 17 years old and attached 70 scalp electrodes to each of them.

They then showed them either a simple auditory tone, an image or a tone combined with an image and told them to press a button as soon as they heard the noise, saw the image or experienced both. They found that the more time it took the patients to process the auditory signals, the more severe their autistic symptoms were.

They also found that there was also a smaller correlation between how fast the patients processed the combination of audio and visual signals and the severity of their ASD.

"This is a first step toward developing a biomarker of autism severity — an objective way to assess someone's place on the ASD spectrum," Dr. Molholm said in a statement. "Using EEG recordings in this way might also prove useful for objectively evaluating the effectiveness of ASD therapies."

The EEG recordings might also help physicians diagnose ASD sooner, which in turn leads to earlier treatments and better outcomes. Right now, less than 15 percent of ASD patients are diagnosed before four years of age but this new technology might bring that percentage up.