From the Guidelines
For a paracentesis, the standard labs to order typically include cell count and differential, albumin, total protein, and gram stain and culture, as recommended by the most recent guidelines 1. These tests should be ordered on the ascitic fluid collected during the paracentesis procedure. Additionally, a serum albumin should be ordered to calculate the serum-ascites albumin gradient (SAAG). The cell count and differential help identify potential infection (spontaneous bacterial peritonitis) if the neutrophil count is elevated. Albumin and total protein levels in the fluid can help determine the cause of ascites, with the SAAG being particularly useful in differentiating portal hypertension from other causes, as supported by previous studies 1. The gram stain and culture are essential for detecting bacterial infections. In some cases, additional tests may be considered based on clinical suspicion:
- Cytology (if malignancy is suspected)
- Amylase (if pancreatic ascites is suspected)
- Triglycerides (if chylous ascites is suspected) These standard labs provide crucial information for diagnosis and management of the underlying cause of ascites, guiding further treatment decisions and interventions. It is also important to note that the initial ascitic fluid analysis should include total protein concentration and calculation of the SAAG, as recommended by the guidelines 1. Other tests, such as ADA assay, may be considered in specific cases, such as suspected tuberculous peritonitis, but their use should be guided by clinical judgment and pre-test probability of specific diagnosis 1.
From the Research
Labs Ordered with Paracentesis
The following labs are typically ordered with paracentesis (percutaneous abdominal paracentesis):
- Serum-ascites albumin gradient (SAAG) to identify portal hypertension-related ascites 2, 3, 4, 5
- Total protein concentration to characterize the ascitic fluid 3
- Cell count and differential to diagnose spontaneous bacterial peritonitis (SBP) 2, 3, 4, 5
- Ascitic fluid polymorphonuclear cell count to diagnose SBP 2, 4
- Ascitic fluid culture to detect infection 4
- Cytology to detect malignant cells 3
- Tumor markers to detect malignant ascites 3
- Lactate dehydrogenase, adenosine deaminase (ADA), triglyceride, amylase, glucose, and brain natriuretic peptide (BNP) may be ordered in specific cases 3
Diagnostic Algorithm
A diagnostic algorithm for patients with new-onset ascites includes:
- Routine ascitic fluid analysis (SAAG, total protein concentration, cell count and differential) 3
- Optional ascitic fluid analysis (cholesterol, fluid culture, cytology, tumor markers, etc.) based on clinical suspicion 3
- Interpretation of ascitic fluid results to determine the etiology of ascites and guide further management 2, 3, 4, 5