Procedures · How much pleural fluid to send
Volume of pleural fluid required to diagnose malignancy
| Design | Prospective comparative study |
|---|---|
| Treatment | Pleural fluid volumes of 60 mL or greater |
| Control | 10 mL sample |
| Population | 121 patient encounters, of which 90 (74.4%) yielded a diagnosis of pleural malignancy |
| Follow-up | Diagnostic study |
| Primary endpoint | Sensitivity and negative predictive value for malignancy by fluid volume |
| Result | For direct smear and cytospin, sensitivity and negative predictive value were significantly higher with 60 mL than with 10 mL (p=0.0058 and p=0.045). Volumes of 10 mL performed worse than larger volumes. |
| Secondary endpoints | Yield by processing method, cell block sensitivity |
The sensitivity for diagnosis of pleural malignancy is dependent on the pleural fluid volume extracted during thoracentesis. Volumes of 10 mL do not perform as well as larger volumes.
The trial authors, in the published abstract
A small practical study with an outsized effect on practice: the volume sent for cytology is a free variable that clinicians control, and getting it wrong costs a repeat procedure.
Swiderek J, Morcos S, Donthireddy V, et al. Prospective study to determine the volume of pleural fluid required to diagnose malignancy. Chest 2010 Jan;137(1):68-73.