Comparison of efficacy of cell block versus conventional smear study in exudative fluids

Cytological examination of serous effusions helps in staging, prognostication and management of patients with malignancy. The method has disadvantage of lower sensitivity in differentiating reactive atypical mesothelial cells from malignant cells.

The aim of this study is to compare the cytological features of pleural and peritoneal exudative fluids by conventional smear (CS) method and cell block (CB) method and also to assess the utility of a combined approach for cytodiagnosis of these effusions.

One hundred and fifty-three pleural and peritoneal exudative fluid samples were subjected to evaluation by both CS and CB methods over a period of 2 years. Cellularity, architecture patterns, morphological features and yield for malignancy were compared, using the two methods. Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy for diagnosing malignancy were calculated by both methods, using histology as a gold standard.

CB method provided higher cellularity, better architectural patterns and additional yield for malignancy as compared to CS method (P < 0.005). Sensitivity, specificity, PPV, NPV, and accuracy by CS method were 69.2%, 95%, 56.25%, 97.08% and 92.8%, while by CB method were 92.30%, 99.2%, 92.30%, 99.28% and 98.6%.

The present study shows that it is advisable to routinely make CBs before discarding specimens that are suspicious for malignancy by smear examination.