title: CA 15-3 as an alternative marker for KL-6 in fibrotic lung diseases.
abstract: BACKGROUND
  KL-6 is a mucin that is increased in interstitial lung diseases (ILD), and in some malignancies. CA 15-3, a tumor marker for breast cancer, refers to the same mucin but utilizes antibodies against different epitopes.
  
  
  OBJECTIVE
  The aim of our study was to evaluate CA 15-3 as a viable alternative to KL-6 as a for ILDs with and without fibrosis.
  
  
  METHODS
  Serum from 242 patients with ILDs and from 327 healthy controls were included and KL-6 and CA 15-3 were measured in all subjects. Regression analyses and ROC curves were used to compare the performances of both markers.
  
  
  RESULTS
  KL-6 and CA 15-3 levels were both significantly higher in the ILD patients compared to the controls (p < 0.0001). A weak yet significant correlation was found between serum KL-6 and CA 15-3 levels in the controls (R = 0.39, p < 0.0001), but showed a much higher correlation in the patient group (R = 0.85, p < 0.0001). CA 15-3 correlated best with KL-6 in patients with fibrotic ILDs (R = 0.83, p < 0.0001). KL-6 performed better as a marker compared to CA 15-3 in most ILDs. Both markers performed best in identifying idiopathic pulmonary fibrosis (IPF) and were equally able to differentiate between ILDs with and without fibrosis: (sensitivity and specificity %): 100/97, 95/92, and 90/72, respectively.
  
  
  CONCLUSIONS
  CA 15-3 and KL-6 are equally sensitive and specific in terms of differentiating between ILDs with and without fibrosis. The wide availability, ease of use, and cost effectiveness, make CA 15-3 a viable alternative for KL-6 as a possible marker for pulmonary fibrosis.
authors.affiliation: Department of Clinical Chemistry, St Antonius Hospital, Koekoekslaan 1, 3435 CM, Nieuwegein, The Netherlands.
authors.forename: A
authors.initials: A
authors.lastname: Kruit
authors.forename: W B M
authors.initials: WB
authors.lastname: Gerritsen
authors.forename: N
authors.initials: N
authors.lastname: Pot
authors.forename: J C
authors.initials: JC
authors.lastname: Grutters
authors.forename: J M M
authors.initials: JM
authors.lastname: van den Bosch
authors.forename: H J T
authors.initials: HJ
authors.lastname: Ruven
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000542:Alveolitis, Extrinsic Allergic / Q000097:blood; D015415:Biomarkers / Q000097:blood*; D005260:Female; D006801:Humans; D017563:Lung Diseases, Interstitial / Q000097:blood*; D008297:Male; D008875:Middle Aged; D018396:Mucin-1 / Q000097:blood*; D012372:ROC Curve; D055815:Young Adult
chemical_list: D015415:Biomarkers; C060192:MUC1 protein, human; D018396:Mucin-1