Statistical analysis:
We used non-parametric statistics due to the non-normal distribution of BAL cytology results. Two sample Wilcoxon- rank sum (Mann-Whitney) test was used to study statistical significance comparing groups. For correlation, Spearman’s rank test was used for non-parametric correlation and Chi-square for 2 categorical variables. A p-value <0.05 was considered significant. Cell counts are presented as median percent and range. Analyses were conducted with STATA 9 (StataCorp-Texas,USA ).