Only 20 percent of children with persistent asthma have a level of control that is optimal, according to a study published today in the journal of Ambulatory Pediatrics. The study revealed that 37 percent received no preventive medication, despite current guidelines that recommend it to all children with persistent asthma; shockingly, another 43 percent did receive medications, but were still troubled by poor symptom control, regardless of the child's age or the household's income level.