Patient demographics and clinical characteristics, stratified by MBL concentration, are summarized in Table 1 . The prevalence of MBL deficiency was 0.5%, 1.9%, 24.2%, or 52.3%, when deficiency was defined as #50, #100, #500, or .50 and #1000 ng/mL, respectively (Table 1) . Regardless of the concentration of MBL used to define MBL deficiency, no difference was observed with respect to the prevalence of MBL deficiency by gender, race, or age (with the exception that a greater fraction of women had MBL deficiency defined as .50 ng/mL and #1000 ng/mL than was seen with the other definitions), smoking status, chronic bronchitis, or steroid use, and there was no suggestion that airflow limitation was worse or that GOLD (Global Initiative for Chronic Obstructive Lung Disease) stage was higher in subjects with MBL deficiency ( Table 1 ). The same findings were also observed for the subgroups of subjects receiving azithromycin or placebo (data not shown).