title: Increased levels of KL-6 and subsequent mortality in patients with interstitial lung diseases.
abstract: OBJECTIVE
  KL-6 is a specific marker in patients with interstitial lung diseases (ILDs); however, the relationship between elevated levels of KL-6 and subsequent mortality is not well defined. To determine if elevated serum levels of KL-6 are associated with increased mortality, and to identify the most suitable cut-off level of KL-6 by which to distinguish between good prognosis and poor prognosis, we evaluated the prognostic significance of serum KL-6 levels in patients with stable-state ILDs.
  
  
  METHODS
  Two hundred and nineteen patients diagnosed with ILDs (152 with idiopathic interstitial pneumonia and 67 with collagen disease-associated pulmonary fibrosis) at Tsukuba University Hospital from April 1999 to October 2005 were entered in this study. Serum KL-6 levels in patients with ILDs were measured with a commercially available enzyme immunoassay kit, and these patients were then followed up.
  
  
  RESULTS
  During the follow-up period, 58 of the 219 patients died of respiratory failure. Patients who died during this period had higher levels of KL-6 than did those who did not (P = 0.0004). The receiver operating characteristic curve analysis showed 1000 U mL(-1) as the most suitable cut-off level by which to distinguish between the two groups of patients. The 95% specificity serum KL-6 level with poor outcome was 2750 U mL(-1). In univariate and multivariate analysis, elevated serum KL-6 (>1000 U mL(-1)) in the stable state indicated poor prognosis (P = 0.0005, log-rank test; P = 0.0001, Cox proportional hazard model).
  
  
  CONCLUSIONS
  Elevated KL-6 level may provide simple, yet valuable information by which to identify patients with ILDs who are at increased risk for subsequent mortality.
authors.affiliation: Division of Respiratory Medicine, Institute of Clinical Medicine, University of Tsukuba, Tsukuba City, Ibaraki, Japan. hirosato@md.tsukuba.ac.jp
authors.forename: H
authors.initials: H
authors.lastname: Satoh
authors.forename: K
authors.initials: K
authors.lastname: Kurishima
authors.forename: H
authors.initials: H
authors.lastname: Ishikawa
authors.forename: M
authors.initials: M
authors.lastname: Ohtsuka
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000951:Antigens, Neoplasm / Q000097:blood*; D005260:Female; D006801:Humans; D007564:Japan / Q000453:epidemiology; D017563:Lung Diseases, Interstitial / Q000097:blood / Q000175:diagnosis / Q000401:mortality*; D008297:Male; D008875:Middle Aged; D018396:Mucin-1; D009077:Mucins / Q000097:blood*; D011379:Prognosis; D011446:Prospective Studies; D011658:Pulmonary Fibrosis / Q000097:blood / Q000175:diagnosis / Q000401:mortality; D012372:ROC Curve; D012680:Sensitivity and Specificity; D018709:Statistics, Nonparametric; D014797:Vital Capacity
chemical_list: D000951:Antigens, Neoplasm; C060192:MUC1 protein, human; D018396:Mucin-1; D009077:Mucins