title: KL-6: a serological biomarker for interstitial lung disease in patients with polymyositis and dermatomyositis.
abstract: OBJECTIVE
  To investigate whether Caucasian patients with polymyositis (PM) or dermatomyositis (DM) and interstitial lung disease (ILD) have elevated serum levels of KL-6 compared with patients without ILD and whether KL-6 could be used as a marker for ILD activity and treatment efficacy of ILD in PM/DM.
  
  
  METHODS
  Thirty patients with PM/DM (seven with ILD) and 17 age- and sex-matched healthy controls were included in a retrospective, cross-sectional analysis. Twelve patients were followed for longitudinal evaluation. ILD was defined as restrictive lung function impairment with radiographic signs of ILD. Serum KL-6 levels were measured using a sandwich enzyme immunoassay kit. Groups were compared by Mann-Whitney U-test.
  
  
  RESULTS
  PM/DM patients with ILD had significantly higher median serum KL-6 levels compared with those without ILD: 995 (range 533-2318) versus 322 (range 132-1225) U mL(-1) (P = 0.0002). Median serum levels of healthy controls were 225 (range 136-519) U mL(-1) . Serum levels of KL-6 were inversely correlated with percentages of forced expiratory volume in 1 s (FEV1), vital capacity (VC), total lung capacity (TLC), forced VC, diffusing capacity of carbon monoxide (DLco), maximal voluntary ventilation at 40 breaths min(-1) and residual volume (RV). Changes in KL-6 levels showed a significant inverse correlation with changes in percentage FEV1, TLC, DLco and RV. At a cut-off level of 549 U mL(-1) (mean ± 2.5 SD for controls), the sensitivity and specificity for diagnosis of ILD were 83% and 100%, respectively.
  
  
  CONCLUSIONS
  The level of serum KL-6 may serve as measure of ILD in patients with PM/DM and is a promising biomarker for use in clinical practice to assess clinical response to treatment.
authors.affiliation: Department of Respiratory Medicine and Allergy, Karolinska University Hospital, Solna, Sweden. maryam.fathi@karolinska.se
authors.forename: M
authors.initials: M
authors.lastname: Fathi
authors.forename: S
authors.initials: S
authors.lastname: Barbasso Helmers
authors.forename: I E
authors.initials: IE
authors.lastname: Lundberg
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D016022:Case-Control Studies; D003430:Cross-Sectional Studies; D003882:Dermatomyositis / Q000150:complications / Q000175:diagnosis / Q000276:immunology*; D004359:Drug Therapy, Combination; D042241:Early Diagnosis; D005260:Female; D005500:Follow-Up Studies; D005938:Glucocorticoids / Q000627:therapeutic use; D006801:Humans; D007166:Immunosuppressive Agents / Q000627:therapeutic use; D017563:Lung Diseases, Interstitial / Q000150:complications / Q000175:diagnosis* / Q000188:drug therapy / Q000276:immunology*; D008297:Male; D008875:Middle Aged; D018396:Mucin-1 / Q000097:blood*; D017285:Polymyositis / Q000150:complications / Q000175:diagnosis / Q000276:immunology*; D011237:Predictive Value of Tests; D011379:Prognosis; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric; D016896:Treatment Outcome; D044465:White People
chemical_list: D015415:Biomarkers; D005938:Glucocorticoids; D007166:Immunosuppressive Agents; C060192:MUC1 protein, human; D018396:Mucin-1