FRAILTOOLS study protocol: a comprehensive validation of frailty assessment tools to screen and diagnose frailty in different clinical and social settings and to provide instrument... oleh Marta Checa-López, Myriam Oviedo-Briones, Armando Pardo-Gómez, Jimmy Gonzales-Turín, Tania Guevara-Guevara, José Antonio Carnicero, Shirley Alamo-Ascencio, Francesco Landi, Matteo Cesari, Tomasz Grodzicki, Leocadio Rodriguez-Mañas, on behalf of FRAILTOOLS consortium