Chronic obstructive pulmonary disease history assessment in Spain: a multidimensional chronic obstructive pulmonary disease evaluation. Study methods and organization.

INTRODUCTION: This present paper describes the method and the organization of the study known as the COPD History Assessment In SpaiN (CHAIN), whose main objective is to evaluate the long-term natural history of a chronic obstructive pulmonary disease (COPD) patient cohort from a multidimensional standpoint and to identify clinical phenotypes, in comparison with another non-COPD control cohort. PATIENTS AND METHODS: CHAIN is a multicenter, observational study of prospective cohorts carried out at 36 Spanish hospitals. Both cohorts will be followed-up during a 5-year study period with complete office visits every 12 months and telephone interviews every 6 months in order to evaluate exacerbations and the vital state of the subjects. The recruitment period for cases was between 15 January 2010 and 31 March 2012. At each annual visit, information will be collected on: (i) clinical aspects (socio-economic situation, anthropometric data, comorbidities, smoking, respiratory symptoms, exacerbations, quality of life, anxiety-depression scale, daily life activities, treatments); (ii) respiratory function (spirometry, blood gases, hyperinflation, diffusion, respiratory pressures); (iii) BODE index (main study variable); (iv) peripheral muscle function, and (v) blood work-up (including IgE and cardiovascular risk factors). In addition, a serum bank will be created for the future determination of biomarkers. The data of the patients are anonymized in a database with a hierarchical access control in order to guarantee secure information access. The CHAIN study will provide information about the progression of COPD and it will establish a network of researchers for future projects related with COPD.