Amylase levels in pleural effusions: a consecutive unselected series of 841 patients

Abstract

Study objectives: To describe the causes and relative frequency of amylase-rich pleural effusion (ARPE), and to study the origin and histologic type of the tumors with ARPE, the strength of the association between ARPE and the result of pleural cytology, and whether pleural amylase (PA) is a prognostic factor in the survival of patients with a malignant pleural effusion.

Setting: Tertiary-care, university-affiliated hospital.

Patients: Eight hundred forty-one consecutive patients with pleural effusion prospectively assessed from 1991 to 1999.

Results: There were 66 ARPEs: 40 neoplastic, and 26 benign with tuberculosis, pancreatitis, and liver cirrhosis as the most frequent causes. Thirty-six percent of patients in our series and 61% of patients with ARPE had a neoplastic disease (odds ratio [OR], 3; p < 0.001); this association got much stronger for cases with PA levels > or = 600 IU/L (95th percentile); [OR, 10; p < 0.001]. The most frequent tumor origin was lung cancer (13 cases). Adenocarcinoma was the most frequent histologic type (18 cases). Two mesothelioma effusions were ARPEs. There was a positive association between ARPE and the finding of tumor cells in pleural fluid (OR, 2.79; p < 0.01). In the malignant group, PA levels > or = 600 IU/L identified a group of patients with quite a short median survival (p = 0.016).

Conclusions: The most common cause of ARPE was neoplasm. There was a positive association between ARPE and malignancy, stronger with the highest levels (95th percentile). Lung cancer and adenocarcinoma were the most common tumor and histologic type associated with ARPE. Mesothelioma may also produce ARPE. There was an association between ARPE and the finding of tumor cells in the pleural fluid. The highest PA levels identified a group of patients with a median shorter survival.