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.Materials and 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.

Root cause analysis of indeterminate diagnoses in serous fluids cytopathology

“…Wu et al evaluated 74 patients whose effusions were divided to three volumes as 25, 50, 125 mL. Although detection rate of malignant cells increased from 88% to 100% with increased volume, the findings were not statistically significant to suggest one group over the other 18 . Thomas et al concluded in their analysis that the sensitivity did not increase after 50 mL, 19 and Abouzgheib suggested 25 to 50 mL would be sufficient for high sensitivity 20 .…”

A 2‐year retrospective study on pleural effusions: A cancer centre experience

“…Other factors which influence the diagnostic yield include specimen handling, volume of fluid submitted and extent of pleural involvement . As for the minimal volume necessary for proper fluid interpretation, there is relatively strong evidence in the literature that a minimal range volume of around 50‐75 mL should be adopted, to diminish potential false negatives and optimise the test sensitivity . Determination of volume submitted for examination was beyond the scope of the current study, but clinicians at our hospital tend to send all aspirated volume for analysis in the laboratory and therefore this should not be a factor contributing for our non‐diagnostic rate.…”

Collection and Handling of Thoracic Small Biopsy and Cytology Specimens for Ancillary Studies: Guideline From the College of American Pathologists in Collaboration With the American College of Chest Physicians, Association for Molecular Pathology, American Society of Cytopathology, American Thoracic Society, Pulmonary Pathology Society, Papanicolaou Society of Cytopathology, Society of Interventional Radiology, and Society of Thoracic Radiology

“…Although the systematic review identified 3 prospective cohort studies [104][105][106] and 4 retrospective cohort studies [107][108][109][110] that all reported on minimum volume of fluid required for a diagnosis, the expert panel believed there was too much heterogeneity within the identified studies upon which to base an evidence-based statement. Additionally, no study reported on an upper limit of fluid.…”