The Association Between the Ratio of Cytology Volume to Thoracentesis Volume and Malignancy Detection

Sumartono AHI¹, Pitoyo CW², Susanto YDB³, Muhadi M⁴

¹Department of Internal Medicine, Faculty of Medicine, Universitas Indonesia, Cipto Mangunkusumo National General Hospital, Jakarta, Indonesia

²Division of Pulmonology and Critical Care Medicine, Department of Internal Medicine, Faculty of Medicine, Universitas Indonesia, Cipto Mangunkusumo National General Hospital, Jakarta, Indonesia

³Department of Anatomical Pathology, Faculty of Medicine, Universitas Indonesia, Cipto Mangunkusumo National General Hospital, Jakarta, Indonesia

⁴Division of Cardiovascular Medicine, Department of Internal Medicine, Faculty of Medicine, Universitas Indonesia, Cipto Mangunkusumo National General Hospital, Jakarta, Indonesia

Corresponding author: Adwin Haryo Indrawan Sumartono, E-mail: adwinsumartono@yahoo.com

ABSTRACT

Background: Pleural effusion cytology is a primary method to identify malignant pleural effusion. While the volume of fluid submitted for cytology may influence malignancy detection, the relationship between the ratio of cytology fluid volume to thoracentesis volume and malignancy detection remains unclear.

Objective: To assess the association between the ratio of cytology fluid volume to thoracentesis volume and malignancy detection.

Methods: An observational cross-sectional study was conducted at Cipto Mangunkusumo National General Hospital from January 1 to October 31, 2023. Inclusion criteria were patients with suspected malignant pleural effusion who underwent thoracentesis and cytology examination. Exclusion criteria included a history of malignant pleural effusion, more than one cytology examination with discordant results, and incomplete data. Bivariate analysis used the Kruskal-Wallis test, followed by multivariate analysis to control confounders. The optimal fluid ratio cutoff was determined using ROC curve analysis.

Results: Among 174 subjects, malignancy was detected in 26.4% of cases. Adenocarcinoma (25.9%) and breast cancer (12.1%) were the most frequently identified types and primary sites. The AUC was 0.629, with an optimal fluid ratio cut-off of 0.022 (sensitivity 62%, specificity 63%). A fluid ratio <0.022 increased the risk of malignancy detection (PR 1.647; 95% CI: 1.204–2.252; p=0.002). A thoracentesis volume >680 mL with a cytology volume of 15 mL was associated with increased malignancy detection.

Conclusion: There is an association between the cytology fluid volume-to-thoracentesis fluid volume ratio with malignancy detection, which is influenced by the total thoracentesis volume. A fluid ratio <0.022 and thoracentesis volume >680 mL with a cytology volume of 15 mL increase the likelihood of detecting malignancy.

Keywords: fluid volume ratio, cytology, thoracentesis, malignant pleural effusion