1. Division of Pulmonary, Critical Care, Allergy and Sleep Medicine, Medical University of South Carolina, Charleston, South Carolina, USA
2. Servico de Analisis Clinicos, Complexo Hospitalario Clinico, Universitario de Santiago, Santiago de Compostela, A Coruña, Spain
3. Servicio de Neumologia, Complexo Hospitalario Clinico, Universitario de Santiago, Santiago de Compostela, A Coruña, Spain