Laboratory Tests for Tumor Lysis Syndrome
Monitor uric acid, potassium, phosphorus, calcium, creatinine, BUN, and LDH every 6 hours for the first 24 hours in established TLS, then daily thereafter, with high-risk patients requiring monitoring every 12 hours for the first three days before TLS develops. 1, 2
Core Laboratory Panel
The essential laboratory tests for diagnosing and managing TLS include:
- Uric acid: Elevated if increased by >25% from baseline or absolute values ≥476 mmol/L (8 mg/dL) 2
- Potassium: Elevated if increased by >25% from baseline or absolute values ≥6.0 mmol/L (6 mEq/L) 2
- Phosphorus: Elevated if increased by >25% from baseline or values ≥1.45 mmol/L (4.5 mg/dL) in adults and ≥2.1 mmol/L (6.5 mg/dL) in children 3, 2
- Calcium: Decreased if decreased by >25% from baseline or values ≤1.75 mmol/L (7 mg/dL) 3, 2
- Creatinine and BUN: For assessing renal function 1, 2
- LDH: Reflects tumor burden and is a key predictor of TLS risk 3, 1
Diagnostic Criteria
Laboratory TLS is diagnosed when two or more of the above metabolic abnormalities occur within three days before or seven days after starting anticancer treatment. 2 Clinical TLS requires laboratory TLS plus at least one clinical complication: renal failure (eGFR ≤60 mL/min), cardiac arrhythmia, or seizure. 3, 2
Monitoring Frequency Algorithm
For High-Risk Patients (Before TLS Develops):
- Monitor LDH, uric acid, sodium, potassium, creatinine, BUN, phosphorus, and calcium every 12 hours for the first three days, then every 24 hours subsequently 1, 2
For Established TLS:
- Monitor vital signs, serum uric acid, electrolytes, and renal function every 6 hours for the first 24 hours, then daily thereafter 1, 2
- Additional parameters including complete blood count, serum LDH, albumin, serum osmolality, blood gases, ECG, and body weight should be assessed every 24 hours 2
Renal Function Assessment
Calculate estimated glomerular filtration rate (eGFR) using either the MDRD formula or Cockroft-Gault equation to reliably assess renal excretion function. 3, 1
The MDRD formula: eGFR (mL/min/1.73 m²) = 175 × (serum creatinine (mmol/L) × 0.0113)^-1.154 × age (years)^-0.203 × (0.742 if female) 3
The Cockroft-Gault equation: (140-age) × weight × 1.2 × (0.85 if female) / Serum creatinine (where age is in years, creatinine in mmol/L, weight in kg) 3
Critical Monitoring Considerations
- Urine output: Maintain at least 100 mL/hour in adults (3 mL/kg/hour in children <10 kg), and measure urine osmolality and fractional excretion of sodium to define hydration status 2
- Continuous ECG monitoring: Required in all hyperkalemic patients 4
- Avoid calcium gluconate for mild asymptomatic hypocalcemia, as it increases tissue and renal calcium phosphate precipitation 4, 2
Common Pitfalls
Do not alkalinize urine in patients receiving rasburicase therapy, as it increases calcium phosphate precipitation and reduces xanthine solubility without providing clinical benefit. 4 Serum creatinine is a poor biomarker for acute kidney damage, making eGFR calculation essential for accurate assessment. 3 When using rasburicase, plasma uric acid levels can be maintained at ≤2 mg/dL in 96% of patients within 4 hours of the first dose. 5