What tests should be ordered for diagnostic paracentesis (percutaneous abdominal fluid aspiration)?

From the Guidelines

For diagnostic paracentesis, the essential tests to order include ascitic fluid neutrophil count, ascitic fluid total protein, ascitic fluid albumin, and serum albumin to calculate the serum-ascites albumin gradient, as recommended by the American Association for the Study of Liver Diseases in 2021 1. When performing diagnostic paracentesis, it is crucial to prioritize tests that provide immediate and relevant information for patient management. The tests mentioned above are fundamental in diagnosing the cause of ascites and detecting potential complications.

• The ascitic fluid neutrophil count helps in identifying spontaneous bacterial peritonitis (SBP), a condition that requires prompt antibiotic treatment.
• The serum-ascites albumin gradient (SAAG) is vital in differentiating between portal hypertension-related ascites and non-portal hypertension causes, guiding further management and treatment decisions. Additional tests may be ordered based on clinical suspicion, such as amylase and triglycerides for pancreatic ascites, cytology for malignancy concerns, or fungal cultures when fungal peritonitis is suspected, as outlined in the 2021 practice guidance by the American Association for the Study of Liver Diseases 1. However, these should be guided by the patient's clinical context and not routinely performed.
• The guidance provided in 1 emphasizes the importance of tailoring diagnostic tests to the individual patient's risk factors and clinical presentation, ensuring that resources are used efficiently and effectively. By following this approach, healthcare providers can ensure that patients receive appropriate and timely care, improving outcomes and quality of life.

From the Research

Diagnostic Tests for Paracentesis

The following tests should be ordered for diagnostic paracentesis:

• Cell count, including polymorphonuclear cell count to diagnose spontaneous bacterial peritonitis 2, 3
• Protein level, including total protein concentration and serum-ascites albumin gradient (SAAG) to classify ascites into portal hypertensive and non-portal hypertensive 2, 4, 5, 3
• Culture, including fluid culture to determine the presence of organisms and the severity of peritonitis 4, 6
• Optional tests, including:
  • Cholesterol, lactate dehydrogenase, adenosine deaminase (ADA), triglyceride, amylase, glucose, brain natriuretic peptide (BNP) 4
  • Cytology, tumor markers 4, 6

Interpretation of Test Results

The results of these tests can be used to:

• Diagnose spontaneous bacterial peritonitis, with a neutrophil count ≥250 cells/mm3 being highly suggestive 2, 3
• Classify ascites into portal hypertensive (SAAG >1.1 g/dl) and non-portal hypertensive (SAAG <1.1 g/dl) 2, 4, 5, 3
• Determine the underlying etiology of ascites, with the SAAG being the most useful test in identifying portal hypertension-related ascites 3