To choose the cut-off point of ferritin for differentiation between benign from malignant pleural-peritoneal effusion

To explore the level of ferritin for differentiating the benign from malignant pleural and peritoneal effusion, 218 pleural-peritoneal effusion samples from patients with different kinds of diseases were determined for ferritin (PFt) by RIA, in the meanwhile serum ferritin (SFt) was also determined. According to clinical diagnosis, these samples were divided into two groups: benign and malignant. PFt and SFt were compared between these two groups, and the ratio of PFt to SFt was counted. The ROC curve was used to choose the best cut-off point PFt for differentiating benign from malignant pleural and peritoneal effusion. The results showed that in the benign effusion group the PFt was 142.4±38.6 μg/L, SFt was 89.7±43.5 μg/L, and PFt/ SFt was 1.46±0.55, whereas in the group of malignant effusion the corresponding figures were 576.5±239.l μg/L, 189.±81.7 μg/L, and 3.67±1.48, respectively. The cut-off point for differentiating benign from malignant pleural and peritoneal effusion was 400 μg/L. Our differentiation standards are: PFt≥400 μg/L,PFt/SFt≥3 for the malignant pleural and peritoneal ef- fusion, and PFt<400 μg/L, PFt/SFt<3 for the benign effusion. The sensitivity is 84.5%, the specificity is 87.5%, and the accuracy is 92.8%. (authors)