Serum and Ascitic Procalcitonin Levels in Cirrhotic Patients with Spontaneous Bacterial Peritonitis: Diagnostic Value and Relationship to Pro-inflammatory Cytokines

Objective: To assess the potential role of procalcitonin and pro-inflammatory cytokines, TNF-alpha, and IL-6, in the diagnosis of spontaneous bacterial peritonitis (SBP).

Design: Prospective study.

Setting: The emergency unit of a teaching hospital.

Patients: We included 21 patients with SBP and 40 patients with sterile ascitic fluid.

Interventions: None.

Measurements And Main Results: For the diagnosis of SBP, the best markers were serum levels of procalcitonin with a cut-off value of 0.75 ng/ml, a sensitivity of 95%, a specificity of 98%, and ascitic fluid levels of IL-6 with a cut-off value of 5,000 ng/ml, a sensitivity of 100%, and a specificity of 88%. C-reactive protein and serum polymorphonuclear count have low sensitivity/specificity at 62/92% and 57/90%, respectively. From 21 patients with SBP, ascitic fluid to serum ratio of TNF-alpha and IL-6 was greater than to 2 in all cases with a mean at 6.2 +/- 6.5 and 34 +/- 31, respectively. By contrast, this ratio for procalcitonin was less than 1 in all cases with a mean at 0.31 +/- 0.25. We found no correlation between procalcitonin levels and cytokine levels in either ascitic fluid or serum.

Conclusions: Serum procalcitonin level may become a useful marker for the diagnosis of SBP in cirrhotic patients. The low ratio of ascitic fluid to serum procalcitonin supports the hypothesis that procalcitonin is not produced intraperitoneally.