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-α, 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 5000 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-α 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.