SAAG (Serum-Ascites Albumin Gradient)
SAAG (Serum-Ascites Albumin Gradient) - a deterministic tool in Sophie Well's Clinical Scoring & Risk group.
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What this is
Calculate the serum-ascites albumin gradient (SAAG) by subtracting the ascitic-fluid albumin from a serum albumin drawn on the same day. A SAAG >=1.1 g/dL indicates portal hypertension (cirrhosis, heart failure, Budd-Chiari, massive hepatic metastasis, alcoholic hepatitis, or fulminant hepatic failure); a SAAG <1.1 g/dL points to non-portal causes (peritoneal carcinomatosis, tuberculous peritonitis, pancreatic or biliary ascites, nephrotic syndrome, or serositis). Sophie Well returns the gradient to one decimal and labels the portal-hypertensive band. Source: Runyon BA. Hepatology 1992;16:240-245.
When to use it
Use this on the initial diagnostic paracentesis for new-onset ascites, and on any subsequent paracentesis where the etiology is uncertain or the clinical picture is changing. The SAAG has effectively replaced the older transudate/exudate framework for ascitic fluid because it discriminates portal hypertension from non-portal causes with about 97% accuracy. Pair the gradient with the absolute ascitic protein (>=2.5 g/dL with high SAAG suggests cardiac ascites; low total protein with high SAAG suggests cirrhosis and predicts spontaneous bacterial peritonitis risk) and the cell count and differential before settling on a single etiology.
References
Runyon BA. Hepatology 1992;16:240-245.
Worked example: SAAG 2.0 g/dL - portal hypertension.
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