Gil-Guillén et al. BMC Public Health 2011, 11:413 http://www.biomedcentral.com/1471-2458/11/413 Table 2 Study variables in FUMEPOC study Variables Socio-demographic Smoking status Pack-year index = (no cigarettes per day/20) × smoking years Symptoms (morning cough, sputum) and others (specify) Spirometer device COPD-6 (FEV 1, FEV 6 and FEV1/FEV6) Evaluation of screening test results Personal history and cardiovascular diseases Consultation Time (physician) Referral Time (patient) Collection method Clinical record Clinical record Clinical record Clinical record Device result Test Clinical record Timer/Chronometer (minutes) Days Cholesterol (HDL and LDL), PAS, PAD, BMI Laboratory results taken from the clinical record WHO’s Smoking and tobacco Use Policy. A smoker is defined as someone who smokes any tobacco product, either daily or occasionally. Statistical Analysis Univariate and bivariate analysis will be performed to describe the variables and to analyze validity indicators. For those related to the spyrometers’ screening, the sen- sitivity, specificity, positive predictive value and negative predictive value (PPV and NPV) and likelihood ratio will be calculated; for the values of the diagnostic tests which follow a quantitative scale the ROC curve (recei- ver operating characteristic) will be used in order to facilitate the cut-off point. Confidence interval is used at 95% for all variables. Ethical and Legal Issues The FUMEPOC study protocol has been reviewed and approved by the Committee for Ethics and Clinical Trials of San Juan Hospital (Comite Ético de Investiga- ción Clínica (CEIC) de Hospital de San Juan) Legal Aspects The study is conducted according to the standards of the International Guidelines for Ethical Review of Epide- miological Studies (Council for International Organiza- tions of Medical Sciences- CIOMS-Geneva, 1991) and the recommendations of the Spanish Society of Epide- miology about the review of ethical aspects of epidemio- logical research. Confidentiality of the data All information relative to the patient’s identity is considered confidential. The data generated during the study will be handled according to the Spanish Law 5/1999 and corresponding norms. All of the researchers will be required to sign a confidential- ity agreement in order to access the study data. Page 3 of 6 Informed consent All patients must read the “Patient Information Form” and sign a document giving in consent. Discussion COPD is a leading cause of morbidity and mortality worldwide, and results in an economic and social bur- den that is both substantial and increasing. The preva- lence and morbidity data greatly underestimate the total burden of COPD because the disease is usually not diag- nosed until it is clinically apparent and moderately advanced [2]. Currently, COPD is a more costly disease than asthma and, depending on country 50-75% of the costs are for health services associated with exacerbations. Tobacco smoke is by far the most important risk factor for COPD worldwide. Other important risk factors are occupational exposures, socio-economic status and genetic predisposition [2]. COPD is the fourth-leading cause of death in the USA and Europe, and COPD mortality in females has more than doubled over the last 20 yrs [13]. This study is developed in the Health Departments of San Juan and Elda (Alicante, Spain), with enough research personnel and material resources for its imple- mentation (spirometers-CS-, COPD-6 spirometers, clini- cal rooms, and others). Family doctors of these Departments will perform the study once a training course was made. An early diagnosis of COPD is important, since depending on the stage in which it is made, different treatments or actions can be applied. This is important because currently there are no treatments that can reverse the natural history of disease in later stages [6,7]. Some limits of this diagnostic tests study are related to those from diagnostic observational studies for the vali- dation of a measure device, such as diagnosed verifica- tion bias. It must be taken into account to consider the validity of the results. In order to solve some kind of bias some measures will be taken. Both tests should be applied to all patients (positive and negative screening results) in order to obtain the diagnoses confirmation or not in all cases. Patients were selected from Primary care setting by their family doctors so the percentage of non-responders is expected to be low avoiding selection bias. This study includes only smokers because of the increased risk for COPD but in the future and depend- ing on the results a second phase will be conducted with ex-smokers. The “gold standard test” should be applied blindly to the evaluator that is not aware of the outcome of the screening test in order to avoid information bias. So that, the COPD6 result will be not included in the