Diagnostic Criteria for Tumor Lysis Syndrome
The Cairo-Bishop criteria define tumor lysis syndrome through two distinct categories: Laboratory TLS (LTLS) requires two or more abnormal metabolic values, while Clinical TLS (CTLS) requires LTLS plus at least one significant clinical complication. 1
Laboratory Tumor Lysis Syndrome (LTLS)
LTLS is present when two or more of the following serum abnormalities occur within 3 days before or 7 days after initiating anticancer treatment:
- Uric acid: ≥8 mg/dL (476 μmol/L) OR 25% increase from baseline 1, 2
- Potassium: ≥6.0 mEq/L (6.0 mmol/L) OR 25% increase from baseline 1, 2
- Phosphorus: ≥4.5 mg/dL (1.45 mmol/L) in adults OR ≥6.5 mg/dL (2.1 mmol/L) in children OR 25% increase from baseline 1, 2
- Calcium: ≤7 mg/dL (1.75 mmol/L) OR 25% decrease from baseline 1, 2
The key advantage of the Cairo-Bishop system over earlier classifications is that it accounts for patients who present with TLS before treatment initiation or develop it after 4 days, and it doesn't require a 25% change if absolute values are already abnormal 1.
Clinical Tumor Lysis Syndrome (CTLS)
CTLS requires the presence of LTLS PLUS one or more of these clinical complications: 1, 2
- Renal insufficiency: Estimated glomerular filtration rate (eGFR) ≤60 mL/min
- Cardiac arrhythmias or sudden death
- Seizures
Important Caveat About Renal Assessment
The expert panel consensus emphasizes that serum creatinine alone is inadequate for evaluating renal dysfunction in TLS because it depends on age, hydration status, and muscle mass 2. Instead, glomerular filtration rate should be estimated using:
- MDRD formula: eGFR (mL/min/1.73 m²) = 175 × (serum creatinine × 0.0113)^-1.154 × age^-0.203 × (0.742 if female) 2
- Cockcroft-Gault equation: (140-age) × weight × 1.2 × (0.85 if female) / serum creatinine 2
Grading System
- LTLS: Present or absent (binary classification) 1
- CTLS: Graded I-IV based on the maximal severity of clinical manifestations 1, 2
Clinical Context and Timing
Symptoms typically occur 12-72 hours after initiating cytoreductive therapy, though they can occur before treatment starts 1. The Cairo-Bishop timeframe of 3 days before to 7 days after treatment initiation captures the vast majority of cases and addresses the shortcomings of earlier systems that only considered a 4-day window 1.
Critical Pitfall
Clinical TLS carries significantly higher mortality than laboratory TLS alone. In one study, CTLS was associated with an 83% death rate versus 24% for LTLS (P < .001), with CTLS being a major cause of death in many patients 1. This underscores why the distinction between laboratory and clinical TLS is clinically meaningful—LTLS may not require aggressive intervention, but CTLS represents a life-threatening emergency requiring immediate management 1.
The Cairo-Bishop criteria remain the most widely accepted classification system and are incorporated into major clinical trials 1, 3, 4, 5, 6.