title: The clinical utility of pleural YKL-40 levels in diagnosing pleural effusions.
abstract: OBJECTIVE
  Recent evidence suggests that YKL-40 is a relatively new biomarker of inflammation and it is involved in the pathogenesis of several pulmonary diseases. Details of serum and pleural YKL-40 in pleural effusions however, remain unknown. We aimed to assess whether serum and pleural YKL-40 is an accurate biomarker of pleural effusions.
  
  
  METHODS
  This clinical study was prospective, observational and cross-sectional. The concentrations of serum and pleural fluid YKL-40 and conventional pleural marker levels were measured in 80 subjects with pleural effusions, including 23 transudates caused by congestive heart failure (CHF), and 57 exudates including 23 parapneumonic, 22 malignant and 12 tuberculous pleural effusions (TBPEs).
  
  
  RESULTS
  Median pleural fluid YKL-40 levels were higher in exudates than in transudates (219.4 and 205.9 ng/mL, respectively, P<0.001). High pleural YKL-40 levels, with a cutoff value of >215 ng/mL, yielded a 73% sensitivity, 73% specificity, likelihood ratio 2.8 for diagnosing exudate, with an area under the curve of 0.770 [95% confidence intervals (CI): 0.657-0.884]. Pleural YKL-40/serum YKL-40 ratio >1.5 yielded a 75% sensitivity, 72% specificity and likelihood ratio 2.6 for diagnosing TBPE, with an area under the curve of 0.825 (95% CI: 0.710-0.940).
  
  
  CONCLUSIONS
  High concentrations of pleural YKL-40 level may help to differentiate exudate from transudate and a high pleural YKL-40/serum YKL-40 ratio may be helpful in seperating TBPE from non-tuberculous effusions.
authors.affiliation: Department of Pulmonary Medicine, Recep Tayyip Erdogan University, Rize, Turkey;
authors.forename: Servet
authors.initials: S
authors.lastname: Kayhan
authors.forename: Aziz
authors.initials: A
authors.lastname: Gumus
authors.forename: Halit
authors.initials: H
authors.lastname: Cinarka
authors.forename: Naci
authors.initials: N
authors.lastname: Murat
authors.forename: Adnan
authors.initials: A
authors.lastname: Yilmaz
authors.forename: Recep
authors.initials: R
authors.lastname: Bedir
authors.forename: Unal
authors.initials: U
authors.lastname: Sahin
keywords: Exudate; YKL-40; pleural effusion; transudate; tuberculosis