What serum-ascites albumin gradient (SAAG) is indicative of cirrhosis?

Serum-Ascites Albumin Gradient (SAAG) in Cirrhosis

A SAAG >11g/L (or ≥1.1 g/dL) is consistent with the diagnosis of cirrhosis. 1

Understanding SAAG and Its Diagnostic Value

The serum-ascites albumin gradient (SAAG) is a valuable diagnostic tool that helps differentiate the causes of ascites. It is calculated by subtracting the ascitic fluid albumin concentration from the serum albumin concentration.

SAAG Classification:

• High SAAG (≥1.1 g/dL or ≥11 g/L): Indicates portal hypertension, typically seen in:

  • Cirrhosis
  • Alcoholic hepatitis
  • Heart failure
  • Budd-Chiari syndrome

• Low SAAG (<1.1 g/dL or <11 g/L): Indicates causes unrelated to portal hypertension:

  • Malignancy (peritoneal carcinomatosis)
  • Tuberculosis
  • Nephrotic syndrome
  • Pancreatic ascites

Evidence Supporting SAAG in Cirrhosis Diagnosis

Multiple studies have confirmed that SAAG is superior to the traditional exudate-transudate classification based on ascitic fluid total protein (AFTP) 2. The diagnostic accuracy of SAAG for portal hypertension-related ascites is remarkably high:

• Sensitivity: 97%
• Specificity: 95%
• Positive predictive value: 98.6%
• Negative predictive value: 90%
• Overall diagnostic accuracy: 96% 1

In contrast, the traditional ascitic fluid total protein method has significantly lower diagnostic efficacy:

• Sensitivity: 53%
• Specificity: 70%
• Diagnostic accuracy: 56% 1

Clinical Applications and Limitations

Strong Correlation with Portal Hypertension

SAAG correlates well with portal hypertension in cirrhotic patients. Studies have shown that 84.6% of patients with cirrhosis have a high SAAG (≥1.1 g/dL) 3.

Prediction of Esophageal Varices

A high SAAG is also useful in predicting the presence of esophageal varices in patients with ascites:

• 91% of cirrhotic patients with high SAAG have esophageal varices
• Only 50% of cirrhotic patients with low SAAG have esophageal varices 3

Limitations and Pitfalls

• False low SAAG can occasionally occur in cirrhotic patients. In one study, 15.4% of patients with confirmed cirrhosis had a low SAAG 3.

• When a low SAAG is found in a patient with known cirrhosis, consider:

  1. Spontaneous bacterial peritonitis
  2. Peritoneal carcinomatosis
  3. Nephrotic syndrome 4
  4. Laboratory error

• A repeat paracentesis is recommended when a low SAAG is found in a patient with known cirrhosis, as 73% of such patients will show a high SAAG on repeat testing 4.

Conclusion

When evaluating ascites, SAAG provides critical diagnostic information about the underlying pathophysiology. A SAAG ≥1.1 g/dL (≥11 g/L) strongly supports portal hypertension as the cause of ascites, which is typically seen in cirrhosis. This makes option A (SAAG >11g) the correct answer for the diagnosis of cirrhosis.