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Asthma In America is one of the largest and most comprehensive national surveys ever conducted about asthma. The survey is actually composed of three separate surveys, each based on telephone interviews with national probability samples of three populations:
- Current asthma patients, defined as persons who had been diagnosed with asthma and who had either experienced asthma symptoms or taken medication for asthma within the past year. A total of 2,509 cases of current asthma, including 1,788 adults with asthma and the parents of 721 children with asthma, were interviewed. This sample was identified by systematically screening a geographically stratified national sample of 42,022 U.S. households by telephone.
- Healthcare providers, including 512 physicians, 101 nurses and 113 pharmacists. National probability samples were drawn from each of these populations. The physician sample was further stratified to represent primary care specialties and specialists in asthma care.
- Although doctors report that they are following NHLBI guidelines and patients are generally satisfied with their care, the level of care reported by patients does not meet current standards.
- General adult population of the United States, with 1,000 completed interviews.
The interviews were conducted by telephone from May 21 to July 7, 1998. The patient interview averaged 30 minutes in length, the general public interview averaged 16 minutes in length, and the healthcare provider interviews averaged 17-21 minutes in length. The completed samples were weighted to correct for any disproportionate sampling or unequal probabilities of selection so that the weighted survey results should yield unbiased national estimates.
The maximum expected sampling error for a simple random sample of 500 (e.g., doctor survey) is ± 4.4 percentage points at the 95% confidence level; ± 3.1 percentage points at the 95% confidence level for a sample of 1,000 (e.g., public survey); and ± 2.0 percentage points at the 95% confidence level for a sample of 2,500 (e.g., patient survey).
Although there have been a number of asthma surveys during the past decade, Asthma In America may be considered a landmark study in asthma research because:
- The patient survey is one of the largest, if not the largest, national probability survey of both adults and children with asthma. The sample size (N=2,509) is large enough to yield precise estimates of the total population of patients.
- The survey is one of the most comprehensive ever conducted among a national sample. The 30-minute patient interview covers a broader range of subjects, including symptoms, morbidity, treatment and quality of life, in more depth than any previous large-scale survey of which we are aware.
- The questionnaires for the surveys of the healthcare providers and the general public were designed to permit comparisons with patient responses. The study therefore offers insight into the different perspectives of patients and providers on treatment and other issues.
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