http://www.niddk.nih.gov/health/digest/pubs/celiac/index.htm states the following:
In Italy, where celiac disease is common, all children are screened by age 6 so that even asymptomatic disease is caught early. In addition, Italians of any age are tested for the disease as soon as they show symptoms. As a result of this vigilance, the time between when symptoms begin and the disease is diagnosed is usually only 2 to 3 weeks. In the United States, the time between the first symptoms and diagnosis averages about 10 years.