Figure 4.
The average change in z score for forced expiratory volume in t seconds, where t is either 0.75 or 1 (zFEVt) in health and cystic fibrosis. Slope (zFEVt/yr) estimates were derived from an interaction term between diagnosis group and age using a mixed-effects model with repeated measures of zFEVt where random intercepts only were specified. Although the intercepts differed between health and cystic fibrosis, the rate of decline in zFEVt was similar in both groups. CF = cystic fibrosis subjects; HC = healthy control subjects.