[Diagnosis of spontaneous ascites infection in patients with cirrhosis: reagent strips]

Abstract

Aim: To evaluate the sensitivity, specificity, and predictive values of dipstick testing (DT) for detecting spontaneous bacterial peritonitis (SBP), defined by an ascites neutrophil polymorphonuclear cell count > or = 250/mm3, in patients with cirrhosis.

Methods: The study includes all patients with cirrhosis and ascites admitted to our general hospital on the southern outskirts of the Paris metropolitan area (France) from June 2003 to May 2004 (n = 47:27 men and 20 women). Diagnostic abdominal paracentesis was performed on admission, and a Multistix SG (Bayer Pharma) reagent strip was immersed in one ascitic sample from each patient. Readings after 120 s were either negative (DT-) or positive (DT+, with 4 levels of positivity: trace, +, ++, or +++). In case of cytologically-proven SBP, patients were treated with cefotaxime, and subsequent paracentesis with DT and cytologic testing took place every 48 hours, until recovery.

Results: Six of the 47 patients had proven SBP, all with clinical signs of SBP (fever and/or abdominal pain); five of these patients were DT+ and one was DT-. In the five patients initially DT+, the DT became negative at the same time as the cytologic criteria for SBP disappeared. Forty-one patients did not meet the cytologic criteria for SBP: 34 were DT- and 7 were DT+ (traces: 4, ++: 2, +++:1); two of these had clinical signs suggestive of SBP.

Conclusion: Although the sensitivity (83%), specificity (83%) and negative predictive value (97%) of DTwere satisfactory, its positive predictive value (42%) was low. Dipstick testing of ascitic fluid is easy to perform and inexpensive and may be recommended for diagnosis and follow-up of SBP, especially in emergency settings.