Such patients often are referred to in the United States as having asthmatic bronchitis or the asthmatic form of COPD. Persons with chronic bronchitis and/or emphysema without airflow obstruction (ie, subsets 1, 2, and 11) are not classified as having COPD. Patients with airway obstruction due to diseases with known etiology or specific pathology, such as cystic fibrosis or obliterative bronchiolitis (subset 10), are not included in this definition. Reprinted with permission from the American Thoracic Society. of a hospital or other specialist visit (ie, inpatient, outpatient, or in an accident and emergency unit) must be recorded when the GP is informed. The diagnosis, symptoms, procedure or investigation, referrals, and their outcome must be entered into the relevant sections of the medical record. In this report, estimates are presented for patients who attended their GP, were given a diagnosis of asthma or COPD, and were registered throughout 1998. Pulmonary function data are not systematically or routinely available.
Case Definitions
Definitions of OLD in each database differ. NHANES III was a survey, and the questionnaire part of the survey asked participants about self-reported physician-diagnosis of three conditions (ie, asthma, chronic bronchitis, and emphysema). A positive response to the single question “Has a doctor ever told you that you have emphysema?” was sufficient to define emphysema. But, for asthma and chronic bronchitis, positive responses to the following two questions were necessary to define a current condition: “Has the doctor ever told you that you have [asthma or chronic bronchitis]?” and ”Do you still have it?“ A participant could be classified as having ah three conditions.
The GPRD system uses the Oxford Medical Information System (OXMIS) and READ coding system (the first three digits of the OXMIS number corresponds, in most cases, to the first three digits of the International Classification of Diseases, eighth revision, codes). Physician-diagnosed asthma, chronic bronchitis, and emphysema were defined as any individual who was labeled with one or more of the OXMIS/READ codes that were compatible with their respective diagnoses during calendar year 1998. This permitted the use of terms like COPD without reference to chronic bronchitis or emphysema. Acute bronchitis was excluded from the algorithm. The choice of GPRD OXMIS/ READ codes was recorded by each individual GP without instructions or guidelines. Direct codes for COPD were defined as overlapping chronic bronchitis and emphysema in the Venn diagrams.
Spirometry in NHANES III
Lung function testing was conducted on participants aged > 8 years by a trained technician in a mobile examination center (MEC). Testing also was conducted at the home of participants aged > 60 years who were unwilling or unable to come to the MEC.