title: Adenosine deaminase levels in nontuberculous lymphocytic pleural effusions.
abstract: OBJECTIVE
  Adenosine deaminase (ADA) can aid in the diagnosis of tuberculous pleural effusions, but false-positive findings from lymphocytic effusions have been reported. We studied the ADA levels in a variety of nontuberculous lymphocytic effusions and analyzed the relationships between ADA and conventional hematologic and biochemical parameters.
  
  
  METHODS
  One hundred six lymphocytic pleural fluid samples (lymphocyte count > 50%) were analyzed. These included post-coronary artery bypass grafting (CABG) effusions (n = 45), malignant effusions (n = 27), miscellaneous exudative effusions (n = 10), and transudative effusions (n = 24). ADA levels were determined using the Giusti method. In 22 randomly selected cases, ADA was measured again on the same sample 6 weeks later.
  
  
  RESULTS
  The ADA level reached the diagnostic cutoff for tuberculosis (40 U/L) in only three cases (2.8%): two lymphomas and one complicated parapneumonic effusion. There was no significant correlation between effusion ADA levels and the total leukocyte (r = 0.08), differential lymphocyte (r = 0.18) or monocyte (r = - 0.18) counts. ADA levels were significantly lower in the transudative effusions (7.2 +/- 3.5 U/L) than in post-CABG (16.6 +/- 7.2 U/L), malignant (15.3 +/- 11.2 U/L), and other exudative (15.4 +/- 13.1 U/L) effusions (p < 0.001). ADA measurements were consistent when assayed 6 weeks apart (r = 0.95; p < 0.00001; coefficient of variation, 14%).
  
  
  CONCLUSIONS
  ADA levels in nontuberculous lymphocytic effusions seldom exceeded the diagnostic cutoff for TB. Effusion ADA levels cannot be predicted from total or differential leukocyte counts. Post-CABG pleural fluids had ADA levels similar to other nontuberculous lymphocytic effusions. ADA is stable in effusion fluids, and its measurement is reproducible.
authors.affiliation: Department of Pulmonary Medicine, St. Thomas Hospital and Vanderbilt University, Nashville, TN 37202, USA. ycgarylee@hotmail.com
authors.forename: Y C
authors.initials: YC
authors.lastname: Lee
authors.forename: J T
authors.initials: JT
authors.lastname: Rogers
authors.forename: R M
authors.initials: RM
authors.lastname: Rodriguez
authors.forename: K D
authors.initials: KD
authors.lastname: Miller
authors.forename: R W
authors.initials: RW
authors.lastname: Light
mesh_terms: D000243:Adenosine Deaminase / Q000032:analysis*; D001026:Coronary Artery Bypass; D005122:Exudates and Transudates / Q000201:enzymology; D006801:Humans; D007958:Leukocyte Count; D008214:Lymphocytes; D008223:Lymphoma / Q000201:enzymology; D010996:Pleural Effusion / Q000201:enzymology*; D016066:Pleural Effusion, Malignant / Q000201:enzymology
chemical_list: D000243:Adenosine Deaminase