SAAG Calculator – Serum-Ascites Albumin Gradient

The SAAG calculation relies on a straightforward subtraction formula. You take the albumin concentration measured in your blood serum and subtract the albumin concentration measured in the ascitic fluid obtained via paracentesis. The mathematical representation is: Gradient = Serum Albumin - Ascites Albumin. A result of 1.1 g/dL or greater strongly indicates that the ascites is due to portal hypertension, such as cirrhosis or heart failure, whereas a gradient below 1.1 g/dL points to non-portal hypertensive etiologies like peritoneal carcinomatosis or nephrotic syndrome.

Imagine a patient undergoes a diagnostic paracentesis and routine blood work. Laboratory results return a serum albumin level of 3.8 g/dL and an ascitic fluid albumin level of 2.2 g/dL. To find the gradient, apply the formula: SAAG = 3.8 - 2.2 = 1.6 g/dL. Because the resulting value of 1.6 g/dL is well above the critical threshold of 1.1 g/dL, it strongly indicates that the patient's ascites is secondary to portal hypertension.

Ensure that both serum and ascites albumin samples are drawn on the same day to maintain clinical accuracy. Avoid using outdated lab values, as rapid shifts in hydration or diuresis can skew albumin concentrations. Always interpret the SAAG value alongside the total protein count in the ascitic fluid and the patient's overall clinical presentation.