Endotoxin levels in dialysate are measured in which units?

• A. mg/dL
• B. EU/mL
• C. CFU/mL
• D. particles/mL

Answer: (B)

Endotoxin activity is quantified with endotoxin units per milliliter (EU/mL) because the measurement reflects biological pyrogenic activity, not just a chemical mass. The standard assay used is the Limulus amebocyte lysate (LAL) test, which reports results in EU, so dialysate endotoxin levels are expressed as EU/mL. Mass concentrations like mg/dL would measure chemical amount, not endotoxin activity; CFU/mL counts viable bacteria, not endotoxin units; and particles/mL counts particles without indicating endotoxin burden. Keeping endotoxin levels in EU/mL helps ensure patient safety by minimizing pyrogenic reactions during dialysis.