What lab tests are necessary for tumor lysis syndrome?

Laboratory Monitoring in Tumor Lysis Syndrome

Monitor uric acid, potassium, phosphorus, calcium, creatinine, BUN, and LDH at specific intervals based on risk status: every 12 hours for the first 3 days in high-risk patients, then every 24 hours; or every 6 hours for the first 24 hours in established TLS, then daily. 1, 2

Core Laboratory Panel

The essential laboratory tests for tumor lysis syndrome include seven key parameters 2, 3:

• Uric acid - Elevated if increased >25% from baseline or ≥476 mmol/L (8 mg/dL) 3
• Potassium - Elevated if increased >25% from baseline or ≥6.0 mmol/L (6 mEq/L) 3
• Phosphorus - Elevated if increased >25% from baseline or ≥1.45 mmol/L (4.5 mg/dL) in adults, ≥2.1 mmol/L (6.5 mg/dL) in children 3
• Calcium - Decreased if reduced >25% from baseline or ≤1.75 mmol/L (7 mg/dL) 3
• Creatinine and BUN - To assess renal function 1, 2
• LDH - Marker of cellular turnover and disease burden 1, 2

Monitoring Frequency Algorithm

For High-Risk Patients (Before TLS Develops)

• Measure all seven parameters every 12 hours for the first 3 days, then every 24 hours thereafter 1, 2
• High-risk patients include those with bulky disease, high-grade lymphomas, acute lymphoblastic leukemia, elevated baseline LDH, pre-existing renal impairment, or dehydration 1

For Established TLS Patients

• Measure vital signs, serum uric acid, electrolytes, and renal function every 6 hours for the first 24 hours, then daily 1, 2, 3
• Add complete blood count, serum albumin, serum osmolality, blood gases, acid-base status, ECG, and body weight every 24 hours 3
• Maintain continuous ECG monitoring if severe hyperkalemia (≥6 mmol/L) is present 1

Renal Function Assessment

• Calculate estimated glomerular filtration rate (eGFR) using the MDRD formula or Cockroft-Gault equation 2, 3
• Clinical TLS is diagnosed when laboratory abnormalities are accompanied by renal failure (eGFR ≤60 mL/min), cardiac arrhythmias, or seizures 3

Urine Monitoring

• Monitor urine output closely, maintaining at least 100 mL/hour in adults (3 mL/kg/hour in children <10 kg) 3
• Measure urine osmolality and fractional excretion of sodium to define hydration status 3

Diagnostic Criteria

Laboratory TLS requires two or more abnormal values from the four key electrolytes (uric acid, potassium, phosphorus, calcium) within 3 days before or 7 days after starting anticancer treatment 3. This pattern of metabolic derangements results from massive release of intracellular contents into the systemic circulation 4.

Critical Pitfalls to Avoid

• Do not delay monitoring - In rasburicase-treated patients, plasma uric acid can be maintained at normal levels by 4 hours in 72% of patients, emphasizing the need for early and frequent assessment 5
• Avoid calcium supplementation for mild hypocalcemia - This increases tissue and renal calcium phosphate precipitation 3
• Do not alkalinize urine in patients receiving rasburicase therapy 1
• Never co-administer allopurinol with rasburicase - This causes xanthine accumulation and removes substrate for rasburicase 1