Serum KL-6 as a novel disease marker in adolescent and adult cystic fibrosis.

BACKGROUND Cystic fibrosis (CF) is a chronic progressive disease leading to obstructive pulmonary impairment, fibrosis and shortened life expectancy. Serum levels of KL-6, high molecular weight human MUC1 mucin, are increased in the majority of patients with various interstitial lung disorders. Whether they are also elevated in CF has not been investigated before. OBJECTIVE To evaluate whether serum KL-6 levels are elevated and correlate with pulmonary function variables in CF. DESIGN Serum KL-6, lactate dehydrogenase (LDH) and C-reactive protein (CRP) levels were measured in 72 consecutive CF and 80 age- and sex-matched healthy control subjects. The relationship between serum KL-6 levels and pulmonary function variables was analyzed. RESULTS Serum KL-6 levels in CF patients were significantly increased compared to healthy subjects. Receiver operating characteristic curve analysis revealed that the diagnostic accuracy of KL-6 was better than that of LDH and CRP. Serum KL-6 levels showed an inverse relationship with vital capacity (VC) % predicted and forced expiratory volume in one second (FEV1) % predicted. CONCLUSIONS Serum KL-6 levels are elevated and appear to be correlated with pulmonary function variables in CF. These results suggest that KL-6 may be a useful noninvasive marker to monitor disease severity.