title: The minimum volume of pleural fluid required to diagnose malignant pleural effusion: A retrospective study.
abstract: BACKGROUND
  Pleural fluid cytology is a quick and accurate method to diagnose malignant pleural effusions. The optimal volume of fluid for cytological analysis has not yet been identified, and clinical recommendation based on some published clinical experiences has been to send large volumes of fluid for cytological analysis. A quality improvement initiative at our institution was conducted to determine the volume of fluid sufficient for a diagnosis of malignant pleural effusion.
  
  
  METHODS
  The study was approved by the Institutional Review Board. All pleural fluid specimens that were divided into three volumes (25 mL, 50 mL, and 150 mL) and sent for cytological examination were reviewed.
  
  
  RESULTS
  A total of 74 samples from 60 individual patients were evaluable. Thirty-six patients (60%) had a previous diagnosis of malignancy. Of the 74 specimens, 26 (35.1%) were positive for malignancy. The detection rate for malignant pleural effusion by cytology for 25 mL, 50 mL, and 150 mL were 88.5%, 96.2%, and 100.0%, respectively (P= 0.16). Two specimens that were negative in the 25 mL samples turned out to be positive in the 50 mL and 150 mL samples. One specimen was negative in the 25 mL and 50 mL samples but positive in the 150 mL sample.
  
  
  CONCLUSIONS
  Our study did not show any statistically significant difference in the detection of malignant effusion in the 25 mL, 50 mL, and 150 mL group.
authors.affiliation: Department of Medicine, Division of Pulmonary, Critical Care and Sleep Medicine, The George Washington University, Washington, DC 20037, USA.
authors.forename: Huimin
authors.initials: H
authors.lastname: Wu
authors.affiliation: Pulmonary and Critical Care Medicine, Veterans Affairs Medical Center, Washington, DC 20422, USA.
authors.forename: Rahul
authors.initials: R
authors.lastname: Khosla
authors.affiliation: Pulmonary and Critical Care Medicine, Veterans Affairs Medical Center, Washington, DC 20422, USA.
authors.forename: Prashant K
authors.initials: PK
authors.lastname: Rohatgi
authors.affiliation: Pathology and Laboratory Medicine Service, Veterans Affairs Medical Center, Washington, DC 20422, USA; Department of Pathology, The George Washington University, Washington, DC 20422, USA.
authors.forename: Suman S
authors.initials: SS
authors.lastname: Chauhan
authors.affiliation: Pathology and Laboratory Medicine Service, Veterans Affairs Medical Center, Washington, DC 20422, USA; Department of Pathology, The George Washington University, Washington, DC 20422, USA.
authors.forename: Edina
authors.initials: E
authors.lastname: Paal
authors.affiliation: Pathology and Laboratory Medicine Service, Veterans Affairs Medical Center, Washington, DC 20422, USA; Department of Pathology, The George Washington University, Washington, DC 20422, USA.
authors.forename: Wen
authors.initials: W
authors.lastname: Chen
keywords: Cytology; malignant; pleural effusion