How should the white blood cell (WBC) count be interpreted in peritoneal dialysis (PD) fluid?

From the Guidelines

The white cell count in peritoneal dialysate fluid should be interpreted as a key diagnostic indicator for infection, with a count exceeding 250 cells/mm3 (0.25 x 10^9/L) being diagnostic of infection and warranting empiric antibiotic therapy. When analyzing the dialysate fluid, it is essential to consider the clinical context and the presence of symptoms such as fever, abdominal pain, or unexplained deterioration. The white cell count is a rapidly available and accurate indicator of infection, and delaying treatment until culture results are available may result in severe consequences, including mortality 1.

Key considerations when interpreting the white cell count in peritoneal dialysate fluid include:

• A count of 250 cells/mm3 (0.25 x 10^9/L) or higher is indicative of infection and requires empiric antibiotic therapy
• Patients with culture-negative neutrocytic ascites may still require antibiotic therapy, as 34.5% of these patients may become culture-positive
• The presence of symptoms such as fever, abdominal pain, or unexplained deterioration should prompt empiric antibiotic therapy, even if the white cell count is not yet available
• The white cell count should be interpreted alongside clinical symptoms and other diagnostic findings, such as Gram stain results and culture findings 1.

In clinical practice, it is crucial to prioritize the patient's morbidity, mortality, and quality of life when interpreting the white cell count in peritoneal dialysate fluid. Empiric antibiotic therapy should be initiated promptly in patients with suspected infection, and the white cell count should be monitored serially to assess treatment response. This approach is supported by the most recent and highest-quality evidence, which emphasizes the importance of prompt diagnosis and treatment of infection in patients with peritoneal dialysate fluid 1.

From the Research

Interpretation of White Cell Count in Peritoneal Dialysate Fluid

• The diagnosis of peritonitis in peritoneal dialysis patients is based on clinical presentation, dialysis effluent white blood cell (WBC) count, and dialysis effluent culture 2, 3.
• A dialysate white cell count of over 100 cells/μl is commonly used as a diagnostic indicator of peritonitis 2.
• However, a study found that increasing the peritoneal WBC count cutoff to 150,200, and 250/μL provided sensitivity around 98% and gradually increasing specificity 3.
• Another study determined that a peritoneal WBC count cutoff of 230/μL provided specificity of 89% and good positive and negative likelihood scores of 8.3 and 0.03, respectively 3.
• A lower WBC count cutoff point of >79 cells/μL in CAPD fluids may improve sensitivity in predicting CAPD-related peritonitis 4.

Optimal Cutoff Values

• The optimal cutoff value for peritoneal fluid WBC count to diagnose peritonitis is still a matter of debate, with different studies suggesting different values 3, 4.
• A cutoff value of 230/μL has been suggested as a good balance between sensitivity and specificity 3.
• However, a lower cutoff value of >79 cells/μL may be more sensitive in predicting CAPD-related peritonitis 4.

Clinical Implications

• The interpretation of white cell count in peritoneal dialysate fluid should be done in conjunction with clinical symptoms and dialysis effluent culture results 2, 3.
• A high white cell count in the dialysate fluid should prompt further investigation and treatment for peritonitis 2, 3.
• The choice of antibiotic treatment should be guided by the results of dialysis effluent culture and antibiotic sensitivity testing 5, 6.