Ella Balasa blog. Ms. Balasa is ineligible for clinical trials for treatment of symptoms of cystic fibrosis (CF) because most CF studies require participants to have a forced expiratory volume in one second (FEV1) of at least 40 percent, and hers is 25 percent.  She suggests that FEV1 is an insufficient proxy for identifying “healthy” candidates for CF trials, and that current inclusion and exclusion practices be adjusted. (STAT)