Design and operation of the National Asthma Survey.

Objectives: This report presents detailed information on the National Asthma Survey (NAS), a module of the State and Local Area Integrated Survey program conducted by the Centers for Disease Control and Prevention's (CDC) National Center for Health Statistics. NAS, sponsored by the CDC's National Center for Environmental Health, was designed to produce national prevalence estimates of adults and children with asthma; to describe the health, socioeconomic, behavioral, and environmental predictors that relate to controlling asthma better; and to characterize the content of care and limitations of persons with asthma. National prevalence estimates were constructed to be consistent with those produced from the CDC's National Health Interview Survey (NHIS), although prevalence estimates for subpopulations may or may not be consistent with NHIS.

Methods: Two separate random-digit-dial telephone studies were fielded: a national study and a four-state study in Alabama, California, Illinois, and Texas. Children aged 0-17 years and adults aged 18 years and over were included in both studies. The screening procedure differed between the studies. Percentages can be generated for the four states combined or for each state separately. A substudy was conducted in the national study to examine the accuracy of proxy reports of asthma.

Results: Data were collected from February 2003 to March 2004. A total of 955 detailed asthma interviews were completed in the national study and 5,741 in the four-state study. A data file has been released for each study that contains asthma, health, and demographic data, as well as sampling weights. The weighted overall response rates were 47.2% for the national sample and 48.5% for the four-state sample.