Correlation of tumour markers in ascitic fluid and serum: are measurements of ascitic tumour markers a futile attempt?

Correlations between tumour markers in ascitic fluid and serum were investigated to determine whether ascitic fluid analysis had any diagnostic advantage over serum in 91 adults with ascites (55 malign; 36 benign). Serum and ascitic fluid were analysed for carcinoembryonic antigen (CEA), cancer antigen (CA) 125, CA19.9, CA72.4, CA15.3, alpha-fetoprotein (AFP) and cytokeratin-19 fragment (CYFRA). The tumour markers were skewed between the groups so were logarithmically transformed. Correlations between serum and ascitic fluid were tested using Pearson's correlation coefficient. Serum and ascitic fluid levels of CEA, CA125, CYFRA and AFP in the malign group were statistically different and CEA, CA19.9, CA5.3, CYFRA and AFP were statistically different in the benign group. For both groups, all tumour markers were highly correlated in serum and ascitic fluid, with the exception of CYFRA in the malign group. These results indicate that, where malignant ascites is suspected, analysing tumour markers in ascitic fluid does not have any advantage over serum analysis.