Statistical analysis
asthma
REGRESSION, ASTHMA
The comparison of demographic, clinical characteristics and PFTs between the ACS group and the non-ACS group was performed using Wilcoxon rank sum test for continuous variables and Fisher’s exact test for categorical variables. All cytokine levels were log10 transformed. Wilcoxon signed rank test was used to compare cytokines and PFTs from baseline and 2-year follow up for ACS and non-ACS groups separately. Spearman’s rank correlation was used to investigate the correlation between cytokines levels and PFT parameters. Multivariable linear regression models were performed to evaluate the association between differences in PFT parameters and inflammatory markers between baseline and 2 years after adjustment for the intervention (Vitamin D supplementation). The generalized estimating equation (GEE) approach with identity link and working independence correlation structure was used to investigate the effect of ACS and other factors on lung function at baseline and 2 years. The covariates that were significant at the significance level of 0.05 in the univariable analysis (age and FEV1/FVC; asthma and FVC, FEV1; ACS and TLC; randomization and FVC) and additional known confounders were used in the multivariable GEE model. The covariates included age, sex, ACS, asthma, hydroxyurea, inflammatory patterns and lung function and treatment arms. Additional sensitivity analysis with SCD genotype as a covariate was done. Variables with p-value < 0.05 were considered significant. Analysis was performed using R 4.0 and SAS 9.4 (Cary, NC).