Evaluation of leucocyte esterase reagent strip test for the rapid bedside diagnosis of spontaneous bacterial peritonitis.

BACKGROUND Spontaneous bacterial peritonitis (SBP) is a common serious complication of cirrhosis, and carries a high morbidity and mortality. Rapid diagnosis and prompt treatment of this condition may improve survival of such patients. OBJECTIVE To validate the diagnostic efficacy of a leukocyte esterase reagent (LER) strip test for rapid, bedside diagnosis of SBP. METHODS We prospectively studied 175 patients with liver cirrhosis and ascites [mean age 48 (SD 16.4) years; 146 men] between August 2007 and December 2008. Alcohol was the most common (124 of 175; 70.8%) cause of liver cirrhosis. All patients underwent abdominal paracentesis, and the ascitic fluid was processed for cell count, LER strip (Magistik 10) test and culture. Two different cut-offs for calling the LER strip test positive were tried, namely when the color turned light blue [grade 2: >125 polymorphonuclear leucocytes (PMNL)/microL] or it turned purple (grade 3: >500 PMNL/microL). Sensitivity, specificity, positive predictive value, negative predictive value were calculated, using PMN count by microscopy exceeding 250 PMNL/microL. RESULTS LER strip using the more stringent purple-color cut off to diagnose SBP had a sensitivity of 92% and specificity of 100%. The corresponding figures using the light-blue color cut-off were 97% and 89%, respectively. CONCLUSIONS LER strip testing of ascitic fluid is a rapid, cheap and sensitive bed side tool for the diagnosis of SBP.