The serum–ascites albumin gradient (SAAG) is the difference between the concurrently obtained serum albumin concentration and the albumin concentration of the ascitic fluid obtained during paracentesis.
A difference equal to or in excess of 1.1 grams/deciliter (g/dL) indicates portal hypertension as the likely etiology, whereas a gradient which is less than 1.1 g/dL implies an etiology which causes increased vascular permeability in the portal system. A (partial) differential diagnosis of potential etiology, based on the SAAG, is as follows 2:
- serum-ascites albumin gradient > 1.1 g/dL
- serum-ascites albumin gradient < 1.1 g/dL