[Sero-ascitic gradient of albumin: usefulness and diagnostic limitations]

The serum-ascites albumin (SAA) gradient has been defined as the serum albumin concentration minus the ascitic fluid albumin concentration. The SAA gradient is superior to the exudate-transudate concept to classify ascites, being a exact portal hypertension (PH) marker. An elevated SAA gradient (1.1 g/L or greater) correlates with PH, whereas a low gradient indicates no PH. The SAA gradient correlates well with PH in cirrhotic patients. It is also of particular utility to differentiate between congestive heart failure and malignant ascites without liver metastases (both of them with elevated ascites fluid proteins -AFP-). However, a low SAA gradient do not differentiate between tuberculous and malignant ascites. Consequently, there are still need for tests a cytology, culture for mycobacteria or ascites fluid polymorphonuclear cell count in some cases. The level of AFP, apart from the exudate-transudate concept, has some value for certain cases (a low level of AFP implicates a high risk of spontaneous bacterial peritonitis). The SAA gradient should replace the AFP concentration as the initial test to classify ascites.