Rapid detection of spontaneous bacterial peritonitis by granulocyte elastase latex immunoassay and reagent strip

Spontaneous bacterial peritonitis (SBP) is a serious complication in patients with liver cirrhosis that requires rapid recognition for effective antibiotic therapy. Elevated levels of granulocyte elastase (GE), an enzyme that is released from degranulated polymorphonuclear neutrophils(PMN), have been reported in ascitic fluid of SBP patients. The aim of this study was to assess the utility of GE measurement by a latex immunoassay (LIA) and by reagent strips for rapid diagnosis of SBP. In 26 ascitic samples which had differing GE concentrations, the results of this LIA method closely correlated with those of a GE/alpha1-PI complex ELISA and an EIA using monoclonal antibodies against GE. The evaluation parameters of linearity (r > 0.99), analytical recovery (96-107%) and within-assay variation[coefficient of variation(CV): 0.97-2.35%] were found to be satisfactory. In 58 ascitic samples from patients with liver cirrhosis, GE levels confirmed by LIA in SBP ascites (n=14) at the time of diagnosis were higher (1436.9 +/- 715.1 ng/ml) than those in non SBP ascites (n=44)(13.1 +/- 3.9 ng/ml). The receiver operating characteristic (ROC) curve showed that ascitic GE by LIA enabled discrimination between SBP and non-SBP, and a cut-off value of 49.5 ng/ml had a sensitivity of 85.7% and specificity of 97.7%. In addition, the usefulness of reagent strips designed for testing cervical mucus for rapid bedside detection of SBP was assessed for GE. The sensitivity, specificity, and positive and negative predictive values of the reagent strips for diagnosis of SBP were 92.9%, 90.9%, 76.5%, and 97.6%, respectively. These results indicate that GE-LIA and GE reagent strips are rapid and sensitive and can aid diagnosis of SBP.