Diagnostic accuracy of flow cytometry in detecting malignant epithelial cells in serous effusions

Abstract

Introduction: This study aims to evaluate diagnostic accuracy of flow cytometry (FCM) in detecting malignant epithelial cells in serous effusions.

Materials and methods: Flow cytometric assessment of 96 serous fluids (86 ascitic, 10 pleural) was performed by using epithelial cell adhesion molecule (EpCAM) (in all 96 fluids) and MUC-1 (in a subgroup of 40 fluids) as epithelial markers and CD45 and CD14 as leucocyte markers. The percentage of EpCAM positivity and MUC-1 positivity was calculated in the CD14 and CD45 dual negative population by selective gating. The findings were then correlated with the defined gold standard criteria.

Results: The sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and diagnostic accuracy for EpCAM was found to be 92.06%, 96.96%, 98.31%, 86.48%, and 93.75%, respectively, while that for MUC-1 was 79.16%, 93.75%, 95%, 71.4%, and 85%, respectively. The sensitivity, specificity, PPV, NPV, and diagnostic accuracy for dual positivity for EpCAM and MUC-1 was found to be 83.3%, 100%, 100%, 80%, and 90% respectively. On combining FCM with cytomorphology the sensitivity, specificity, PPV, NPV, and diagnostic accuracy all increased greatly to 95.3%, 100%, 100%, 91.4%, and 96.8%, respectively.

Conclusions: This study highlights the importance of multicolored flow cytometric analysis in detecting epithelial malignancies in effusions specially in cases belonging to the atypia of undetermined significance and suspicious for malignancy categories and in cases with strong clinical suspicion of malignancy with negative fluid cytology. We recommend the combined use of FCM and cytology for this specific subgroup of patients in routine clinical practice for fast and accurate reporting.

Keywords: Atypia of undetermined significance; EpCAM; Flow cytometry; MUC1; Serous effusions.