This work was funded by Obra Social y Cultural Cajastur, Fundacion Mutua Madrilena, and by a Grant from the Spanish Ministerio de Sanidad y Consumo (PI03/1439). The CIBERER is an initiative of the ISCIII. Marcos Perez-Basterrechea was awarded a predoctoral grant from the Ministerio de Sanidad y Consumo. The authors acknowledge the technical assistance of Dra. Carmen Garcia Pravia and Paula Busto Martinez.