Gil-Guillén et al. BMC Public Health 2011, 11:413 http://www.biomedcentral.com/1471-2458/11/413 available, and easy to use in primary-care settings. With lower needs of instruction and training in spirometry tech- niques, healthcare providers can easily incorporate spiro- metry into their practices and increase the likelihood of earlier detection of COPD among their patients [10] Therefore, it was decided to develop this study in order to establish the validity and reliability of Vitalo- graph COPD-6 spirometer (COPD-6), and to determine the prevalence of undiagnosed COPD in smokers. The COPD-6 identifies likely cases of COPD by mea- suring patients’ obstructive index and FEV1/FEV6 ratio. Those whose measurements are within normal range can be screened out, allowing diagnostic spirometry resources to be focussed on those most at risk. A pre- vious study about COPD shows acceptable validity indexes but another one shows low sensitivity [11,12]. Methods / Design Main objective To establish the validity and reliability of COPD-6 com- pared with conventional spirometry (CS). Specific objectives 1. To determine the prevalence of undiagnosed COPD in smokers. 2. To establish the saving times in the primary care setting by using COPD-6 before CS instead of CS only. Design FUMEPOC is an observational descriptive study of diag- nostic tests. Setting The sample will be recruited from the province of Ali- cante (Spain) and, specifically, the population receiving healthcare from 5 primary care surgeries at Elda Health Department and San Juan Health Department. So 5 Health centres and 2 Hospitals were involved. Study Population Patients 45 years of age and over who are smokers with a pack-year index greater than 10, without known respiratory disease attending a primary care consultation will be included (Table 1). Patients who refuse to per- form spirometry or not giving in the informed consent were excluded. Table 1 Criteria to include patients in the FUMEPOC study Age 45 years or older Smokers with pack-year index greater than 10 Free of known respiratory disease Informed consent Page 2 of 6 Patients undergo a test with Vitalograph COPD-6 spi- rometer. Subsequently, a spirometry (Datospir-120) will be performed as the gold standard test at the reference hospital and the results will be compared. Patients with acute respiratory disease will make the both tests in a different day once the acute disease has disappeared (at least 6 weeks after acute disease). For sample size calculating, after bibliography search- ing, high variability in sensitivity and specificity criteria was found. For that reason we assume the maximum uncertainty. Thus, the sample size is calculated by accepting a sensitivity or specificity = 50%. A 95% confi- dence level and a 5% precision are assumed. Because of the characteristics of the transversal design of the study, in which patients are screened by the regular family physician, and the absence of complex tests or high-risk tests, we suppose a low percent loss. Therefore we assume a 20% loss. According these assumptions, approximately 480 patients will be needed. Calculations are made with qualitative variables formula for infinite populations in the estimation of a validation parameter (sensitivity / specificity), subsequently the correction for- mula is applied. Methods of Data Collection The number of primary care physicians (PCP) who will participate in the study should be about 40. Each PCP will be trained on the screening tool (COPD-6) and after that will select 10 consecutive patients from daily clinical practice who meet the inclusion criteria (Table 1). Once the patient is included, PCP applied the screening test and asks the patient about some related variables (Table 2). All included patients (screening positive or negative) will be referred to per- form the gold standard test, CS, to be done at the reference Hospital of San Juan or Elda. Figure 1 pro- vides a flow diagram of the study. COPD will be diagnosed according to the most widely accepted criteria, that is, FEV1/FVC < 0.7 and a history of smoking habit. The severity of COPD will be deter- mined according to the GOLD criteria: I (FEV1 > 80%, II (FEV1: 50-80%), III (FEV1: 30-49%); IV (FEV1 < 30%) Vitalograph COPD-6 spirometer. Interpretation of the results The following results were considered: NORMAL (FEV1/FEV6 > 0,7), STAGE I: Mild (FEV1/FEV6 < 0,7 y FEV1 > 80%), STAGE II (FEV1/FEV6 < 0,7 y FEV1 < 80%), STAGE III (FEV1/FEV6 < 0,7 y FEV1 < 50%) and STAGE IV: Severe (FEV1/FEV6 < 0,7 y FEV1 < 30%). Measurements Table 2 shows all the study variables and the collection method. Smoking status will be measured according to