Asthmatic children who are exposed to smoking at home are twice as likely to be readmitted to a hospital for breathing problems, according to a new study Reuters reported.

Researchers from the Cincinnati Children's Hospital Medical Center and Penn State Milton S. Hershey Children's Hospital found that saliva revealed exposure to tobacco smoke in most of the children brought to the hospital for asthma or breathing problems, Reuters reported.

Evidence of nicotine, a chemical in tobacco, in children's saliva is a predictor of whether they would be readmitted to a hospital for asthma-related health problems, compared to the information parents gave to doctors.

"We think saliva is a good and potentially useful test for assessing an important trigger for asthma," Robert Kahn, the study's senior author, told Reuters Health.

For the study researchers examined 619 children admitted to Cincinnati Children's Hospital Medical Center for asthma or other breathing problems between August 2010 and October 2011 between one and 16 years old. They measured the amount of cotinine, a marker for tobacco exposure and  a substance that the body makes when it breaks down nicotine, in the children's blood and saliva samples.

Researchers found that based on reports by the children's caregivers, there appeared to be no correlation between tobacco exposure and hospital readmission. However, when reviewing scientific analysis of saliva, they concluded that secondhand smoking doubles a child's risk of being readmitted to the hospital for asthma within a year, Reuters reported.

Close to 35 percent of parents reported their children having some tobacco exposure, but about 56 percent of the children's blood samples and about 80 percent of their saliva samples revealed that cotinine was in their system.

One in six children involved in the study had to be readmitted to the hospital within a year.

"The ability to measure serum and salivary cotinine levels presents the possibility of an objective measure that can be obtained when a child is seen in the emergency department or in the hospital and may be used to predict future hospitalizations," Kahn, associate director of general and community pediatrics at Cincinnati Children's, said in a statement.