Statistical analysis
The data were analyzed using IBM SPSS Statistics for Windows version 20.0 (IBM Corp., Armonk, NY). Pearson’s chi-square test and Mann–Whitney U test were used for intergroup comparisons of parametric data and nonnormally distributed numerical data, respectively. Independent-samples t test was used to compare demographic data and laboratory parameters between the groups. Wilcoxon analysis was used for intragroup comparisons of laboratory values during follow-up. Pearson correlation analysis was used to evaluate relationships between MCP-1 and SP-A levels and CRP, prothrombin time, D-dimer and PaO2/FiO2. A p-value less than 0.05 was considered statistically significant.