title: Variations in pleural fluid WBC count and differential counts with different sample containers and different methods.
abstract: OBJECTIVE
  To compare the results of pleural fluid analysis for WBC counts and differential cell counts as follows: (1) counting performed manually vs that performed by an automated cell counter; (2) cells collected in different types of specimen containers; and (3) cell counts performed at 4 and 24 h postthoracentesis.
  
  
  METHODS
  Twenty-eight pleural fluid samples were each collected in five different containers (ie, ethylenediaminetetraacetic acid (EDTA)-treated glass, citrate-treated glass, heparinized glass, plain glass, and plain plastic tubes). The WBC counts and differential cell counts were obtained manually (on the EDTA tube) and with an automated counter on all tubes within 4 h of collection, and again after 24 h of refrigeration.
  
  
  RESULTS
  There was a close correlation between the WBC counts obtained manually and those obtained with the automated counter from the pleural fluid samples collected in the EDTA tubes (r = 0.92). With the automated counter, the pleural fluid WBC counts were similar among the three tubes containing anticoagulants, but the counts obtained from the tubes without anticoagulants were significantly lower. The differential cell counts obtained manually and those obtained with the automated cell counter differed substantially. Although the percentage of lymphocytes was similar, the automated counter was inaccurate in differentiating neutrophils from large monocytes or mesothelial cells. The WBC counts obtained within 4 h of collection and 24 h after collection were virtually identical.
  
  
  CONCLUSIONS
  The WBC counts obtained manually and with the automated counter from pleural fluid samples in EDTA tubes correlated very closely. The pleural fluid WBC count was lower if the pleural fluids had been collected in tubes without an anticoagulant. Automated WBC counts from pleural fluid specimens were inaccurate, possibly due to difficulty in separating neutrophils from monocyte/mesothelial cells. Refrigerated storage for up to 24 h had no significant effect on the total WBC count or on the WBC count differential regardless of the tube utilized.
authors.affiliation: Department of Pulmonary Medicine, Saint Thomas Hospital and Vanderbilt University, Nashville, TN, USA.
authors.forename: Barrett D
authors.initials: BD
authors.lastname: Conner
authors.forename: Y C Gary
authors.initials: YC
authors.lastname: Lee
authors.forename: Paul
authors.initials: P
authors.lastname: Branca
authors.forename: Jeffrey T
authors.initials: JT
authors.lastname: Rogers
authors.forename: R Michael
authors.initials: RM
authors.lastname: Rodriguez
authors.forename: Richard W
authors.initials: RW
authors.lastname: Light
mesh_terms: D001800:Blood Specimen Collection / Q000379:methods*; D004492:Edetic Acid; D004804:Eosinophils; D006801:Humans; D007958:Leukocyte Count / Q000295:instrumentation* / Q000379:methods*; D007963:Leukocytes, Mononuclear; D018655:Lymphocyte Count; D009504:Neutrophils; D010996:Pleural Effusion / Q000097:blood* / Q000166:cytology*; D011446:Prospective Studies
chemical_list: D004492:Edetic Acid