A simple checklist that parents could fill out in the waiting room during their baby's one-year checkup could one day help doctors screen for the warning signs of autism earlier than they currently do.

In a new study, researchers found the checklist was a good screening tool for identifying a number of developmental problems in infants.

They say the hope is that if autism could one day be spotted earlier, affected children could enter treatment programs sooner. That should be an advantage since studies have shown that the earlier that children are diagnosed, the better they do.

For the study, 137 San Diego pediatricians tested a 24-question checklist with the parents of more than 10,000 babies. The checklist was written in easy-to-understand terms so that parents could fill it out in about five minutes.

The questionnaire asked about how the babies babbled, gestured and interacted with others. Parents rated their babies on questions such as "When your child plays with toys, does he/she look at you to see if you are watching?" or "Does your child smile or laugh while looking at you?"

Any baby who failed the screening was referred to the University of California, San Diego's autism centre, for more testing. The children were re-tested every six months until age 3, when they were likely to show signs of autism.

Of the more than 10,000 infants, 184 failed the initial screening; 75 per cent ended up being diagnosed with some problem: 32 received an autism diagnosis, 56 had a language delay, 9 were developmentally delayed and 36 were categorized as having some other issue.

But there were problems with the screening test. One in four who failed the initial test were later found to have no problems.

Among those toddlers diagnosed with autism or developmental delay, all of them were referred for behavioural therapy around the age 17 months. So were 89 per cent of those with language delay

On average, the children began receiving treatment at 19 months – much earlier than they would have with current screening tests.

The research was published Thursday in the Journal of Pediatrics.

Neuroscientist Karen Pierce of the University of California, San Diego, who led the study, cited some important limitations to the study.

For example, not all the infants evaluated by the program have been followed for a full three years, so some diagnoses might change.

As well, the investigators noted that more than 1,300 infants actually failed the screening test. But it wasn't clear why only 184 ended up in the evaluation program. The study couldn't tell how much of that gap was recording error, or if families referred themselves for further tests elsewhere.

It's estimated that between one in 100 to 150 children has some form of autism, which ranges from mild to severe and is characterized by difficulties in social interaction and communication.

Doctors and pediatricians are urged to screen for the disorder during regular doctor visits at ages 18 months and 24 months. Yet a 2009 study found that on average, children aren't diagnosed until they're five.

That may be because some doctors don't screen for the condition. Surveys of the doctors recruited for this study showed that most had not been screening infants in any systematic way for autism before they took part in the study.

The screening test is not ready for routine use, as more work is needed to verify its accuracy. But the researchers say their study shows that systematic early screening in pediatricians' offices is feasible.

"There are subtle signs of autism at one year if you just look for them," said Pierce. "Let's just get these kids detected early and treated early."