BackgroundSpontaneous infection of ascites is a severe complication of ascites and must be actively searched for. Many studies have been carried out on inflammatory markers and their levels in serum and ascitic fluid such as complement 3 (C3), complement 4 (C4), high-sensitive C-reactive protein (CRP), and procalcitonin, and have identified their role in the diagnosis of spontaneous bacterial peritonitis (SBP). The aim of our study was to measure and compare the serum and ascitic fluid levels of procalcitonin, high-sensitive CRP, C3, and C4 in patients with SBP and patients without SBP.Patients and methodsThis case–control study was carried out on 10 patients with cirrhotic ascites who were admitted with SBP and 20 patients with cirrhotic ascites with no existing evidence of SBP. Serum and ascitic fluid levels of C3, C4, high-sensitive CRP, and procalcitonin were determined using the enzyme-linked immunosorbent assay method.ResultsThe mean ± SD of the serum levels of C3, C4, high-sensitive CRP, and procalcitonin were 3.38 ± 2.12, 0.36 ± 0.25, 18.76 ± 6.37, and 136.79 ± 58.14, respectively, in group I, whereas their levels in group II were 2.04 ± 1.98, 0.36 ± 0.29, 16.80 ± 5.97, and 147.78 ± 58.65, respectively. The mean ± SD of their ascitic fluid levels were 0.21 ± 0.14, 1.84 ± 1.69, 1.96 ± 1.15, and 162.43 ± 82.51, whereas their levels in group II were 0.46 ± 1.01, 2.07 ± 1.93, 2.98 ± 5.90, and 180.51 ± 93.70, respectively. Surprisingly, all these results were statistically insignificant. However, an ascetic fluid polymorph nuclear leukocyte count higher than 200/mm3 has sensitivity, specificity, positive predictive value, and negative predictive value of 100% in the diagnosis of SBP.ConclusionAn ascitic polymorph nuclear leukocyte count higher than 200/ml was the accurate marker for the diagnosis of SBP.