Diagnostic utility of interferon gamma-induced protein 10 kDa in spontaneous bacterial peritonitis: Single-center study

Background and aims Spontaneous bacterial peritonitis (SBP) is an important cause of mortality and morbidity in cirrhotic patients with ascites. The diagnosis of SBP is mainly made on the basis of a polymorphonuclear leukocyte cell count exceeding 250/μl in ascitic fluid. However, this procedure is subjective. We aimed to evaluate serum and ascitic fluid interferon-γ-induced protein (IP-10) as accurate diagnostic markers for detecting SBP. Methods A total of 425 consecutive patients with ascites were included. Serum and ascitic fluid of IP-10, tumor necrosis factor-α (TNF-α), and interleukin-6 (IL-6) were measured using an enzyme-linked immunosorbent assay. Results Patients were divided into an SBP group, including 61 patients, and a non-SBP group, including 364 patients. Serum and ascitic IP-10 were significantly higher in SBP patients than in patients without SBP (1855±825 vs. 955±510 pg/ml; P<0.001 and 2160±994 vs. 1110±623 pg/ml; P<0.001), respectively. There was a significant increase in both serum and ascitic levels of TNF-α and IL-6 in SBP patients than in patients without SBP. At a cut-off value of 1915 pg/ml, serum IP-10 had 91% sensitivity and 89% specificity for detecting SBP (area under the curve: 0.912). Also, at a cut-off value of 2355 pg/ml, ascitic IP-10 had 92.5% sensitivity and 87% specificity for detecting SBP (area under the curve: 0.943). Both were correlated with ascitic fluid proteins, polymorphonuclear count, TNF-α, and IL-6. Conclusion Serum and ascitic IP-10, TNF-α, and IL-6 are significantly increased in SBP patients versus patients without SBP. Serum level of IP-10 is more specific and sensitive, such as ascites. Thus, it seems to represent a satisfactory diagnostic marker for the diagnosis of SBP.