How this calculator works
Albumin concentrations are converted to g/L before subtraction. A gradient of at least 11 g/L supports portal hypertension as a contributor to ascites; it does not identify a single cause. Negative gradients are retained so that mismatched samples or analytical issues can be reviewed. The result is an estimate for information only and is not medical advice.
Formula
SAAG = serum albumin - ascitic fluid albumin. Serum = SAAG + ascitic albumin. Ascitic albumin = serum - SAAG. The comparison threshold is 11 g/L = 1.1 g/dL.
Worked example
Serum albumin 35 g/L and ascitic albumin 20 g/L give SAAG 15 g/L, or 1.5 g/dL. Serum 2.8 g/dL and ascitic 2.0 g/dL give 0.8 g/dL.
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Frequently asked questions
Must the two samples be contemporaneous?
Yes. The clinical gradient should use serum and ascitic samples obtained at the same time so changes in serum albumin do not distort the comparison.
Is this a protein ratio?
No. It is an albumin concentration difference, with units. Do not divide one albumin value by the other.
Does a high gradient prove cirrhosis?
No. Portal hypertension has several causes, and more than one process may contribute to ascites.