Results
Thirty patients met the inclusion criteria. Brody scores from the CT scans of these patients ranged from 0.46 to 55.30 (median: 19.97, Q1-Q3: 13.80-26.10) out of 100, and ppFEV1 before treatment from 19 to 113 (median: 67, Q1-Q3: 36-83.5). Twenty-three patients with a F508del/F508del genotype had started lumacaftor/ivacaftor, 7 patients with F508del and a gating mutation on the second allele had started ivacaftor. Baseline characteristics for both groups are presented in table 1. Change in ppFEV1 after 6 months of treatment ranged from -19 to +34 (median: +5.0, Q1-Q3: -4.25 - +13). Median change ppFEV1 on ivacaftor was +7 (Q1-Q3:+3 - +27) versus +3 (Q1-Q3:-6 - +11) on lumacaftor/ivacaftor. In the lumacaftor/ivacaftor group, 12 and 11 patients underwent chest CT before and after the start of treatment, respectively.
Brody score (total score without air trapping) correlated significantly with baseline ppFEV1 in patients starting lumacaftor/ivacaftor: Spearman R=-0.514 (p=0.006), Pearson R=- 0.517 (p=0.006).
The correlation between Brody score (total score without air trapping) and change in ppFEV1 after 6 months was not significant: Spearman R=-0.213, (p=0.164), Pearson R=-0.057, (p=0.398). Scatterplots are shown in figure 1.
In patients using ivacaftor, Brody score also correlated significantly with ppFEV1 at baseline, Spearman R=-0.739 (p=0.029), Pearson R=-0.734 (p=0.028). Moreover, in this group there was a significant positive correlation between Brody score and ppFEV1 change after 6 months, with a Spearman R=0.679 (p=0.029) Pearson R = 0.822 (p=0.012). Scatterplots for these correlations are shown in figure 2.
As Brody score in this group is correlated with both ppFEV1 at baseline and ppFEV1 change at 6 months, ppFEV1 at baseline and after 6 months are expected to be interconnected. Therefore we performed a post-hoc analysis calculating the correlation coefficient between ppFEV1 change and Brody score, corrected for ppFEV1 at baseline. The corrected correlation coefficient of R=0.576 in the ivacaftor group still suggests an association, however this result is not statistically significant (p=0.231).