Spontaneous Bacterial Peritonitis: Likelihood Ratios

Introduction: This diagnosis carries a high mortality rate, around 30%. Diagnostic paracentesis is critical in the diagnosis (and may be therapeutic in non-infective ascites).

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Prevalence

Population / Calculator	Prevalence	Comments / Study / Link
Cirrhosis patients admitted to the hospital	27%	JAMA. 2008;299(10):1166-1178. http://jama.ama-assn.org/cgi/content/full/299/10/1166
Cirrhosis patients with prior SBP	0%	Much higher prevalence - these patients are placed on prophylactic antibiotics.
Cirrhosis patients with low ascitic protein	0%	Much higher. These patients get prophylactic antibiotics.
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The likelihood ratios of findings for Spontaneous Bacterial Peritonitis are listed below. See the left navigation bar to change the display.

Pre-Test Probability (Prevalence): %.	Post-Test Probability (Predictive Value): %.	Switch to display mode.
Note that calculating probabilities from more than one** finding is inherently inaccurate because findings are not independent. (For example, using two positive findings that share a common pathogenesis is likely to overestimate the true probability.)

Good Positive and Negative Likelihood Ratios
Finding	Result	+LR	-LR
[ + ] Serum-Ascites Albumin Gradient	+ 0 -	4.5	0.1
>=1.1g/dl Study: JAMA. 2008;299(10):1166-1178. http://jama.ama-assn.org/cgi/content/full/299/10/1166
[ + ] Ascitic Fluid PMN	+ 0 -	10.6	0.2
>500/ul Study: JAMA. 2008;299(10):1166-1178. http://jama.ama-assn.org/cgi/content/full/299/10/1166
[ + ] Ascitic Fluid WBC	+ 0 -	9.6	0.3
>1000/ul Study: JAMA. 2008;299(10):1166-1178. http://jama.ama-assn.org/cgi/content/full/299/10/1166
[ + ] Blood-Ascites pH Gradient	+ 0 -	7.3	0.3
>0.10 Study: JAMA. 2008;299(10):1166-1178. http://jama.ama-assn.org/cgi/content/full/299/10/1166
[ + ] Ascitic Fluid pH	+ 0 -	8.9	0.3
<7.35 Study: JAMA. 2008;299(10):1166-1178. http://jama.ama-assn.org/cgi/content/full/299/10/1166