Context and objective: Spontaneous bacterial peritonitis (SBP) is a frequent and severe complication of cirrhotic patients with ascites. It has been proposed that the reagent strip for leukocyte esterase designed for the testing of urine (Combur test UX) could be a useful tool for diagnosing SPB. The aim of this study was to assess the sensitivity and specificity of urine test strips for diagnosing SBP in cirrhotic patients with ascites.
Design and setting: Prospective study, at a university hospital in northeastern Brazil.
Methods: Forty-two unselected consecutive cirrhotic patients (32 males; mean age: 51.7 +/- years) were included, and a total of 100 paracenteses were performed. All ascitic fluid samples were analyzed using the reagent strip and cytology, neutrophils, lymphocyte count, appropriate biochemical tests and culturing. The strips were considered positive if the color became purple on a colorimetric scale.
Results: Nine patients were diagnosed with SBP using cytology (> 250 neutrophils/mm(3)), and the strips were positive for all these nine patients with SBP. In one sample, the strip was positive but the neutrophil count was less than 250 cells/mm(3). For 86 samples, both the strips and cytology were negative. At the threshold of 250 neutrophils/mm(3) in ascitic fluid, the sensitivity, specificity, positive predictive value and negative predictive value for the strips were respectively 100%, 98.9%, 92.3% and 100%.
Conclusion: The Combur test UX urine screening test is a very sensitive and specific method for diagnosing SBP in cirrhotic patients with ascites.