Not just for IBS / IBD Differentiation
Spontaneous bacterial peritonitis (SBP) is an acute bacterial infection of ascitic fluid. It primarily occurs in patients with advanced cirrhosis and, generally, no source of the infecting agent is easily identifiable.
Fever, abdominal pain, altered mental status, abdominal tenderness, or hypotension in cirrhosis cases indicates SBP. In addition, patients with ascites admitted to the hospital for other reasons should undergo paracentesis to look for evidence of SBP.
Ascites is a major complication of cirrhosis, occurring in about 50% of patients over 10 years of follow up. Its development is associated with a 50% risk of death and signifies the need to consider liver transplantation as a therapeutic option. The majority (75%) of patients who present with ascites have underlying cirrhosis, with the remainder having malignancy, heart failure, tuberculosis, pancreatitis and other rarer causes.
Diagnosis of SBP
If SBP is suspected, a paracentesis should be performed with analysis of the ascitic fluid. It is important that this is done before administration of any antibiotics. Appropriate handling of the ascitic fluid is crucial to minimise the risk of skin flora contaminating the cultures and to avoid obtaining a falsely negative culture. Investigations include aerobic and anaerobic cultures, cell count and differential and fluid chemical analyses (albumin, protein, glucose, lactate dehydrogenase, amylase and, in some cases, bilirubins).
An elevated ascitic fluid absolute Polymorphonuclear (PMN) count (≥ 250/ μl) is adequate to make a presumptive diagnosis of SBP and to start empirical therapy. However, it is common that the paracentesis is performed after antibiotics are initiated and/or an inadequate culture technique is used. In these situations, the cultures are often negative.
Diagnosis can be delayed when laboratory personnel are not readily available or samples are sent to external laboratories.
This is a major drawback, since rapid diagnosis of SBP and early initiation of antibiotic treatment are of paramount importance. Alternative methods using automated PMN counting, reagent strips (urine dipsticks) or ascitic lactoferrin have been developed. Unfortunately, their diagnostic accuracies are limited.
Therefore, an accurate and convenient method of rapid diagnosis of SBP remains an as yet unmet clinical need.
Alpha Laboratories now has the Ascites Calprotectin assay available on the Quantum Blue® quantitative reader. Burri et al.1 recently compared the Quantum Blue Ascites Calprotectin test to an ELISA and to traditional PMN count. They demonstrated that measurement of calprotectin in ascitic fluid correlates well with the PMN count and reliably predicts levels >250/μl. Additionally, they showed that an elevated PMN count could easily be measured by a POC test device. This would enable a treating physician to obtain useful bedside measurements, especially those practicing in settings with limited equipment and/or technical personnel.1
This article was published previously in Alpha Laboratories’ Leading Edge Newsletter – Summer 2014.
1. Burri et al; Measurement of Calprotectin in ascites fluid to identify elevated polymorphonuclear cell count; World J Gastroenterol 2013 April 7; 19(13): 2028- 2036