MUC1 and acute respiratory distress syndrome: BALF KL-6 was detectable in all patients with ARDS (day 0 ARDS median BAL KL-6 concentration, 305 u/ml), and was higher than both control individuals (median = 67 u/ml, 95% CI median difference = 125 to 424, P = 0.002) and at-risk individuals (median = 169.4, 95% CI median difference = 35 to 380, P = 0.008).