Chest
Volume 137, Issue 1, January 2010, Pages 68-73
Journal home page for Chest

Original Research
Neoplastic Disease
Prospective Study To Determine the Volume of Pleural Fluid Required To Diagnose Malignancy

https://doi.org/10.1378/chest.09-0641Get rights and content

Background

The optimal volume of pleural fluid to diagnose a malignant effusion is unknown. Our study was designed to demonstrate if a minimum pleural fluid volume (10 mL) is equivalent to a large volume thoracentesis to make a cytopathologic diagnosis of malignancy.

Methods

A total of 121 thoracentesis samples were obtained from 102 patients with suspected or known malignant effusions. Pleural fluid was collected in three aliquots for cytologic examination (10 mL, 60 mL, ≥ 150 mL). The pathologist was blinded to patient identifiers and aliquot volume. Sensitivity, specificity, negative predictive value (NPV), and positive predictive value (PPV) were calculated for each volume for the diagnosis of malignancy.

Results

Pleural malignancy was diagnosed in 90 patient encounters (74.4%). For direct smear/cytospin, there was increased sensitivity and NPV for 60 mL (P = .0058 and P = .045, respectively) and for ≥ 150 mL (P < .001 and P = .009, respectively) compared with 10 mL. For combined direct smear/cytospin and cell block preparations, statistical significance for sensitivity and NPV existed only between the 10 mL and ≥ 150 mL specimens (P = .0099 and P = .033, respectively). No statistical difference existed for specificity or PPV for any aliquot volume.

Conclusions

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. When both direct smear/cytospin and cell block preparations are used, we recommend ≥ 150 mL, whereas when only direct smear/cytospin is used, 60 mL is adequate for the diagnosis a malignant pleural effusion.

Section snippets

Materials and Methods

This was a single-center prospective study to determine the amount of pleural fluid needed to make the diagnosis of a malignant pleural effusion. The study was performed at Henry Ford Hospital in Detroit, Michigan, and received Institutional Review Board approval. Between September 1, 2001, and August 31, 2007, 102 patients (60 women and 42 men) underwent diagnostic thoracentesis yielding 121 pleural fluid samples. Eligible patients included those suspected of having a malignant pleural

Results

There were 102 patients (42 men and 60 women) in our study population. Table 1 shows our patients' demographic data and past medical history. The average age of our patients in the study was 67.8 years with an SD of 11.6. The difference in the mean age between patients with and without a malignancy was not significant. The mean age of patients with malignancy was 67.4 years (SD, 12.9), whereas the mean age of patients without a malignancy was 68.7 years (SD, 8.0), P = .55. No differences in the

Discussion

The diagnosis of a malignant pleural effusion is a poor prognostic indicator with overall mean life expectancy of approximately 6 months.3 Multiple studies have evaluated the sensitivity of cytologic diagnosis of pleural fluid from thoracentesis fluid sample compared with needle biopsy and thoracoscopy.5, 6, 7, 8, 9, 10, 11, 12, 13 A number of authors have analyzed one or more cytology samples, multiple ways to process the fluid samples for cytologic interpretation, and cytology coupled with

Conclusion

The sensitivity for the diagnosis of a malignant pleural effusion depends on the volume of pleural fluid obtained during thoracentesis. In our study, thoracentesis of at least 60 mL performed better than a 10-mL aliquot of pleural fluid to make the diagnosis of malignancy.

Acknowledgments

Author contributions: Dr Swiderek: contributed to obtaining study patients, delivering specimens to laboratory, blinding all pathology slides prior to interpretation, writing the manuscript, and helping write revisions.

Dr Morcos: contributed to developing initial research protocol, obtaining study patients, and helping write manuscript revisions.

Dr Donthireddy: contributed to developing initial research protocol, obtaining study participants, and helping write manuscript revisions.

Dr Surapaneni:

References (0)

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Funding/Support: This study was funded by the Henry Ford Hospital, Detroit, MI [IRB #1452].

Reproduction of this article is prohibited without written permission from the American College of Chest Physicians (www.chestjournal.org/site/misc/reprints.xhtml).

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