title: Can circulating interleukin-18 differentiate between sarcoidosis and idiopathic pulmonary fibrosis?
abstract: OBJECTIVE
  The aim of the present study was to investigate serum and bronchoalveolar lavage fluid (BALF) interleukin-18 (IL-18) levels in sarcoidosis and idiopathic pulmonary fibrosis (IPF) and to assess the clinical usefulness of IL-18 in these diseases.
  
  
  METHODS
  Serum and BALF levels of IL-18 were measured in 15 patients with sarcoidosis, 10 patients with IPF and 24 control subjects (8 with lung tumor, 6 with pulmonary tuberculosis and 10 healthy controls). Lymphocyte fractions (T, B and natural killer (NK) cells) in blood and BALF were analysed by flow cytometer.
  
  
  RESULTS
  The serum and BALF levels of IL-18 in patients with sarcoidosis were significantly higher (p < 0.05) than those in IPF subjects and control groups. The percentages of T, B and NK cells in blood and BALF did not differ among all groups, while the blood and BALF CD4/CD8 ratios in patients with sarcoidosis were significantly higher (p < 0.05) than those in the other groups. Among all subjects, the serum levels of IL-18 correlated positively with the CD4/CD8 ratios in BALF (r = 0.693, p < 0.001).
  
  
  CONCLUSIONS
  As to the levels of IL-18 in serum and BALF, there were differences between sarcoidosis and IPF indicating a different role of IL-18 in the pathogenesis of these diseases. Measurement of circulating IL-18 might have a potential of clinical utility in the differential diagnosis of sarcoidosis versus IPF.
authors.affiliation: Department of Clinical Laboratory, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China.
authors.forename: Ding-Hua
authors.initials: DH
authors.lastname: Liu
authors.forename: Wei
authors.initials: W
authors.lastname: Cui
authors.forename: Qian
authors.initials: Q
authors.lastname: Chen
authors.forename: Chun-Mei
authors.initials: CM
authors.lastname: Huang
mesh_terms: D000328:Adult; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry / Q000166:cytology; D016516:CD4-CD8 Ratio; D016022:Case-Control Studies; D002681:China; D003937:Diagnosis, Differential; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D054990:Idiopathic Pulmonary Fibrosis / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D020382:Interleukin-18 / Q000097:blood*; D008168:Lung; D008175:Lung Neoplasms / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D018655:Lymphocyte Count; D008297:Male; D008875:Middle Aged; D009169:Mycobacterium tuberculosis / Q000254:growth & development; D017565:Sarcoidosis, Pulmonary / Q000097:blood / Q000175:diagnosis* / Q000276:immunology; D014397:Tuberculosis, Pulmonary / Q000097:blood / Q000175:diagnosis* / Q000276:immunology
chemical_list: D020382:Interleukin-18