The enrollment of patients started on November 1, 2002, and was concluded on July 31, 2003, 9 months later. Consecutive subjects aged from 18 to 65 years and with symptoms suggestive of asthma or COPD (cough, dyspnea, wheezing, chest tightness) without a previous diagnosis were considered. An upper age limit was initially chosen to avoid an excessive bias toward a diagnosis of COPD, since this was not a case finding study but a feasibility and differential diagnosis study. canadian healthcare mall
The study population was randomized 1:1 into two groups (by means of an interactive voice responding system [IVRS]): conventional evaluation without spirometry vs conventional evaluation with spirometry. The size of randomization-balanced blocks was 10 patients within study. Conventional evaluation included case history supported by a questionnaire (for items, see below) and physical examination. Random violation was defined as absence of IVRS code or IVRS treatment code different from actual treatment. Exclusion criteria were a previous diagnosis of asthma or COPD; history of cardiac failure; neuromuscular or autoimmune disorders; present cancer; interstitial lung disease; thoracic surgery in the previous 6 months; present infectious disorders; or respiratory infection in the month before entering the study.
The GPs filled in a form with medical record of the patients (history, risk factors, objective finding, spirometric data according to randomization, diagnosis, and therapy). Risk factors included familiarity; allergy; tobacco smoking; occupational exposure to gas; fumes and inorganic/organic dusts; otorhinolaryngologic comorbidities (rhinitis, rhinorrhea, postnasal drip, polyposis, sinusitis); and gastroenterologic comorbidities (gastroesophageal reflux, hiatal hernia, pyrosis, dyspepsia, epigastric pain). A copy of each form was sent to a coordinating data center.
The patient was then referred to the specialist with only part of the documentation (excluding diagnosis and therapy to which the specialist was blind) in order to have a final diagnosis that was sent to the data center in charge of comparing the diagnosis at the two levels (standard practice vs specialist) and defining the degree of concordance. All pulmonary specialists involved in the study were hospital based or employed in services with full equipment for respiratory function testing. The specialists’ diagnosis was taken as a “gold standard.” The calculation of sample size defined that at least 650 new cases had to be competitively enrolled by GPs to test the null hypothesis (= equivalence of the two diagnostic procedures).
GPs involved in the parallel observational part of the study were given the same exclusion criteria as for the comparative trial, but inclusion criteria were enlarged to also allow patients with a known diagnosis of asthma or COPD on follow-up and there were no upper age limitations. GPs were requested to enroll at least 10 patients. For each patient, they had to fill in a simple form registering age, sex, smoking habits, diagnosis, time for instruction of patient and spirometry performance, and referral to specialist; at the end of the study, a questionnaire was administered to GPs to rate the usefulness of spirometry.