1. What is SAAG? The Serum-Ascites Albumin Gradient (SAAG) is a calculation used to determine the cause of ascites, the accumulation of fluid in the peritoneal cavity. The SAAG is calculated by subtracting the albumin concentration in the ascitic fluid from the albumin concentration in the serum (blood).

Formula: $SAAG = Serum Albumin - Ascitic Fluid Albumin$

2. Purpose of the Test: SAAG is primarily used to differentiate between ascites caused by portal hypertension and ascites caused by other conditions.

High SAAG (≥ 1.1 g/dL): Suggests that the ascites is due to portal hypertension. This can be associated with conditions such as cirrhosis, congestive heart failure, or portal vein thrombosis.
Low SAAG (< 1.1 g/dL): Suggests that the ascites is due to conditions other than portal hypertension, such as infections (e.g., tuberculosis), malignancy, or nephrotic syndrome.