Leucocyte esterase test strips exhibit very poor sensitivity for diagnosis of spontaneous bacterial peritonitis

Introduction: A common problem of patients with cirrhotic ascites is spontaneous bacterial peritonitis (SBP). SBP is a trigger of renal impairment and, if untreated, denotes poor prognosis. Thus, rapid and accurate diagnosis of SBP is pivotal. Diagnosis of SBP is established by >=250 granulocytes/µl in ascitic fluid. Recently, urine reagent strips for leukocyte esterase detection have been proposed as a faster, cheap and accurate method to detect elevated granulocyte count in ascites (Hepatology 2003;37: 893–6).

Methods: Ascitic fluid samples of patients with cirrhotic ascites were examined using two different reagent strip tests, Combur 9 (Roche Diagnostics GmbH) and Multistix SG–10 (Bayer Vital GmbH). Each test was performed simultaneously and independently by two investigators. Standard diagnostics of ascites, including manual granulocyte count, bacterial culture and protein analysis, was carried out in parallel.

Results: 82 paracenteses were performed in 30 patients. SBP was found in 8 samples, 74 samples had <250 granulocytes/µl. A positive test strip result was defined as 2+ or 3+. 6/8 SBP samples had false negative strip tests (1+ or lower), equally for each investigator. In 74 non-SBP samples, 0 to 2 false positive tests results were achieved per investigator. For sensitivity and specifity of the different tests and investigators, see table.

Conclusion: Contrary to previous study results, urine leucocyte test strips lack sufficient sensitivity for elevated granulocyte counts in ascites. Combur test showed better performance than Multistix. Test results of up to 1+, appearing in many SBP-negative ascites samples, did not seem to have diagnostic relevance.

	Combur-Investigator 1	Combur-Investigator 2	Multistix-Investigator 1	Multistix-Investigator 2
Sensitivity	25%	25%	13%	13%
Specifity	99%	97%	99%	97%

leukocyte strip test - sensitivity - spontaneous bacterial peritonitis