What are the typical lab values for tumor lysis syndrome?

Laboratory Values for Tumor Lysis Syndrome

Laboratory tumor lysis syndrome (TLS) is defined by the presence of two or more of the following abnormal serum values occurring within three days before or seven days after the start of anticancer treatment: hyperuricemia, hyperkalemia, hyperphosphatemia, and hypocalcemia. 1

Diagnostic Laboratory Criteria for TLS

Laboratory TLS is characterized by:

• Uric acid: Increase by >25% from baseline or absolute values ≥476 mmol/L (8 mg/dL) 1
• Potassium: Increase by >25% from baseline or absolute values ≥6.0 mmol/L (6 mEq/L) 1
• Phosphorus: Increase by >25% from baseline or absolute values ≥1.45 mmol/L (4.5 mg/dL) in adults and ≥2.1 mmol/L (6.5 mg/dL) in children 1
• Calcium: Decrease by >25% from baseline or absolute values ≤1.75 mmol/L (7 mg/dL) 1

Clinical TLS Definition

Clinical TLS is diagnosed when laboratory TLS is accompanied by at least one of the following clinical complications:

• Renal failure: Estimated glomerular filtration rate (eGFR) ≤60 mL/min 1
• Cardiac arrhythmias: Due to electrolyte abnormalities, particularly hyperkalemia 1
• Seizures: Often related to electrolyte imbalances 1

Assessment of Renal Function

Since renal dysfunction is a critical component of clinical TLS, proper assessment of kidney function is essential:

• Glomerular filtration rate (eGFR) should be calculated using one of these formulas 1:
  • 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) × (1.212 if Black) 1
  • Cockroft-Gault equation: (140-age) × weight × 1.2 × (0.85 if female) / Serum creatinine 1
  • For children: eGFR (mL/min) = 0.55 × length (cm) / serum creatinine (mg/dL) 1

Risk Factors for Developing TLS

Identifying high-risk patients is crucial for prevention:

• Tumor-related factors:

  • Hematologic malignancies with high proliferation rates (Burkitt's lymphoma, B-ALL) 1
  • High tumor burden as indicated by elevated LDH, WBC >50,000/mm³, extensive bone marrow involvement 1

• Patient-related factors:

  • Pre-existing elevated uric acid levels 1
  • Pre-existing renal dysfunction 1
  • Advanced age 1
  • Tumor infiltration in the kidney 1

• Treatment-related factors:

  • Highly active, cycle-specific chemotherapeutic agents (cytosine arabinoside, etoposide, cisplatin) 1
  • Corticosteroid therapy in lymphoid malignancies 1

Clinical Implications

The laboratory abnormalities in TLS can lead to serious clinical consequences:

• Hyperuricemia: Can cause acute uric acid nephropathy due to crystal deposition in renal tubules 2, 3
• Hyperkalemia: May lead to cardiac arrhythmias and sudden death 2, 4
• Hyperphosphatemia: Can cause secondary hypocalcemia and calcium phosphate crystal deposition in tissues 2, 3
• Hypocalcemia: May result in neuromuscular irritability, tetany, and seizures 2, 3

Early recognition of these laboratory abnormalities is essential for prompt intervention to prevent the progression from laboratory TLS to clinical TLS, which carries significant morbidity and mortality 4, 5.