Spontaneous bacterial peritonitis requires an early diagnosis to start antibiotic therapy. The ideal diagnostic study is the cytochemical of ascites fluid, which can be expensive, delayed and of limited availability in primary health care centers. OBJECTIVE:Evaluate the usefulness and diagnostic accuracy of Multistix 10SG test strips for the diagnosis of spontaneous bacterial peritonitis in cirrhotic patients with ascites. MATERIALS AND METHODS:Observational descriptive study of diagnostic test in cirrhotic patients with ascites. The leukocyte count of ascites fluid was determined by the colorimetric scale of the Multistix 10SG test strip and compared with the gold standard for diagnosis (polymorphonuclear ≥ 250 cells / mm³). RESULTS:Of 174 patients with ascites (51.7% women, average age 59 years) 30 were diagnosed with spontaneous bacterial peritonitis. With a grade ++ cut-off point, the test strip had sensitivity 73.3%, specificity 96.5%, positive predictive value 81.4%, negative predictive value 94.5%, positive likelihood ratio 21.2 and negative likelihood ratio of 0.27. CONCLUSIONS:The test strips have adequate specificity and negative predictive value, being a low cost tool, simple use, quick interpretation and easy access, to support the decision not to start an antibiotic in patients with ascites and suspected spontaneous bacterial peritonitis. Due to their low sensitivity they do not replace the cytochemical study as the test of choice for the definitive diagnosis, but it is useful for optimizing the initial approach of these patients.