Comparative Assessment of Two Strategies for Interpreting Tumor Markers in Ascitic Effusions

Abstract

Background/Aim: There are two strategies for the interpretation of tumor markers (TM) in fluid effusions: i) high cutoff and ii) fluid/serum ratio (F/S) and low cutoff. The objective of this study is to compare these two strategies and to determine whether diagnostic accuracy improves by the identification of possible false positives using Adenosine deaminase (ADA), C reactive protein (CRP) and % of polymorphonuclear cells (%PN). Patients and Methods: We studied 157 ascitic fluids, 74 of which were malignant. ADA, CRP and %PN were determined in ascitic fluid, and Carcinoembryonic antigen (CEA), Cancer antigen 72-4 (CA72-4), Cancer antigen CA19-9 and Cancer antigen 15-3 (CA15-3) in both fluid and serum. Results: The strategy of high cutoff showed 59.5% sensitivity at 100% specificity. The F/S strategy showed 75.7% sensitivity at 95.2% specificity. Subclassifying cases with ADA, CRP and %PN negative showed 67.5% sensitivity at 100% specificity for high cutoff and for the F/S strategy was 81.7% sensitivity at 98.7% specificity. Conclusion: The strategy of F/S with negative ADA, CRP and %PN allow the best interpretation for TM in the ascitic fluid. Ascites is the abnormal accumulation of fluid in the peritoneal cavity. It is mostly seen in patients with liver disease, pancreatic disease, tuberculous peritonitis, congestive heart failure, kidney disease, acquired immune deficiency syndrome and cancer (1). Cytology is the gold standard for confirming the presence of malignant cells in ascitic fluid, but its sensitivity only ranges between 50 and 70% (2). The main cause of this low sensitivity is the fact that a primary tumor may infiltrate the peritoneum but may not shed cells, with a negative result in the cytological analysis. In these cases, other invasive procedures, such as laparoscopy may be needed to confirm the presence of malignant cells. The potential of tumor markers (TM) for improving the diagnosis of malignant pleural and peritoneal effusions has been mentioned by several authors but there are major discrepancies between the reports regarding their specificity and sensitivity, and also in terms of the cutoff values used (3-5): for Carcinoembryonic antigen (CEA) the range is 2-50 ng/ml and for Cancer antigen 19-9 (CA19-9) it is 14.5-200 ku/l (6-10). Their sensitivity ranges between 24% and 77% and their specificity from 82% to 100% (6-10).