Statistical Analysis
Descriptive statistics for clinical and demographic characteristics of
the patients are presented as frequency and percentage (%) for
categorical variables and mean with standard deviation (mean ± SD) or
median with interquartile range (median [Q3–Q1]) according to the
distribution of the continuous variables. The normality was assessed
both visually and through the Shapiro–Wilk test. The independent
samples t-test was used to evaluate the intergroup differences for
normally distributed data; lung volumes and densities. For the
parameters which were not normally distributed, Mann–Whitney U test
(Wilcoxon rank-sum test) or Kruskal–Wallis test was used as
appropriate. Pearson Chi-square test was applied to analyze the
categorical variables. The Spearman’s rank correlation coefficients were
used to examine the degree of associations between the right and left
lung densities, and right and left lung volumes and FVC and DLCO
[13]. The test-retest reliability was assessed by the intraclass
correlation coefficient (ICC). The strength of agreement between
repeated measures was determined by an ICC of 0.7 or greater,
representing a high agreement [14]. Statistical analyses were
performed using the SPSS, version 20.0, software (IBM Inc., Chicago, IL,
USA) and RStudio, Version 1.2.1335© 2009-2019 (PBC, Boston, MA).
Two-sided p values less than 0.05 were considered statistically
significant (p <0.05).