Hypernatremia is NOT Included in Tumor Lysis Syndrome Diagnostic Criteria
Hypernatremia (elevated sodium) is definitively excluded from the diagnostic criteria for Tumor Lysis Syndrome. The diagnostic criteria specifically include only four metabolic abnormalities: hyperuricemia, hyperkalemia, hyperphosphatemia, and hypocalcemia 1.
Laboratory Tumor Lysis Syndrome (LTLS) Diagnostic Criteria
The Cairo-Bishop classification system, which represents the current standard for TLS diagnosis, requires two or more of the following abnormalities 1:
- Hyperuricemia (elevated uric acid)
- Hyperkalemia (elevated potassium)
- Hyperphosphatemia (elevated phosphate)
- Hypocalcemia (decreased calcium)
These changes must occur at presentation or change by 25% within 3 days before or 7 days after initiation of treatment 1.
Why Sodium is Not Part of TLS
The pathophysiology of TLS explains this exclusion clearly 2, 3:
- TLS results from rapid tumor cell lysis, which releases intracellular contents into the bloodstream 1, 3
- Intracellular ions released include potassium and phosphate (which are highly concentrated inside cells), not sodium 2, 3
- Sodium is primarily an extracellular ion, so tumor cell lysis does not cause hypernatremia 3
- Nucleic acid breakdown produces uric acid, leading to hyperuricemia 1, 2
- Hyperphosphatemia causes secondary hypocalcemia through calcium-phosphate precipitation 2, 3
Clinical Tumor Lysis Syndrome (CTLS)
CTLS requires the presence of LTLS (the four metabolic abnormalities above) plus one or more clinical complications 1:
- Renal insufficiency
- Cardiac arrhythmias/sudden death
- Seizures
Again, hypernatremia plays no role in this classification 1.
Common Pitfall to Avoid
Do not confuse the fluid management of TLS (which involves aggressive saline hydration) with the diagnostic criteria 1, 4, 5. While aggressive hydration with normal saline is the cornerstone of TLS prevention and treatment, this does not make hypernatremia a diagnostic feature 1, 4, 5. In fact, the goal is to maintain high urine output (≥100 mL/hour in adults) to prevent uric acid and calcium-phosphate precipitation in renal tubules 1, 4.