What are the diagnostic criteria for diabetic ketoacidosis (DKA)?

Diagnostic Criteria for Diabetic Ketoacidosis (DKA)

DKA is diagnosed by the triad of hyperglycemia (blood glucose >250 mg/dL), metabolic acidosis (pH <7.3, bicarbonate <15 mEq/L), and elevated ketones in blood or urine. 1

Classification of DKA Severity

DKA severity can be classified based on arterial pH and serum bicarbonate levels:

Severity	Arterial pH	Serum Bicarbonate (mEq/L)
Mild	7.25-7.30	15-18
Moderate	7.00-7.24	10 to <15
Severe	<7.00	<10

1

Essential Diagnostic Parameters

1. Blood Glucose:

   • Typically >250 mg/dL
   • Note: Euglycemic DKA can occur (especially with SGLT2 inhibitors), where blood glucose may be <200 mg/dL 2

2. Acid-Base Parameters:

   • Arterial pH <7.30
   • Serum bicarbonate <18 mEq/L
   • Anion gap >10-12 mEq/L (calculated as [Na⁺] - [Cl⁻ + HCO₃⁻])

3. Ketones:

   • Positive serum ketones
   • Positive urine ketones
   • Blood β-hydroxybutyrate (BHB) measurement is preferred over urine ketone testing 2
   • BHB level ≥3.0 mmol/L in children and ≥3.8 mmol/L in adults is considered diagnostic 2

4. Serum Osmolality:

   • Variable in DKA (unlike in HHS where it's typically >320 mOsm/kg)
   • Calculated as: 2[measured Na⁺ (mEq/L)] + glucose (mg/dL)/18

5. Mental Status:

   • Can range from alert to drowsy to stupor/coma depending on severity 1

Additional Laboratory Evaluations

When DKA is suspected, the following should be obtained:

• Complete blood count with differential
• Electrolytes (including phosphate, calcium)
• Blood urea nitrogen and creatinine
• Venous or arterial blood gases
• Urinalysis

Important Clinical Considerations

1. Differential Diagnosis:

   • DKA must be distinguished from other causes of high-anion gap metabolic acidosis:
     • Lactic acidosis
     • Salicylate, methanol, ethylene glycol, or paraldehyde ingestion
     • Chronic renal failure (typically hyperchloremic acidosis) 1

2. Monitoring During Treatment:

   • Blood should be drawn every 2-4 hours for:
     • Serum electrolytes
     • Glucose
     • Blood urea nitrogen
     • Creatinine
     • Venous pH (for DKA)
     • Osmolality 1

3. Resolution Criteria:

   • Glucose <200 mg/dL
   • Serum bicarbonate ≥18 mEq/L
   • Venous pH ≥7.3 1
   • BHB <1.5 mmol/L (sensitivity 83%, specificity 87%) 2

4. Special Consideration - Euglycemic DKA:

   • Can occur with SGLT2 inhibitor use
   • Maintain high suspicion in patients with metabolic acidosis and ketosis regardless of glucose levels 2, 3

Pitfalls to Avoid

1. Ketone Measurement Method:

   • The nitroprusside method only measures acetoacetic acid and acetone, not β-hydroxybutyrate (the predominant ketone in DKA)
   • During treatment, β-hydroxybutyrate converts to acetoacetic acid, which may falsely suggest worsening ketosis when using nitroprusside method 1
   • Blood ketone (β-hydroxybutyrate) testing is more reliable than urine ketone testing 2

2. Overlooking Euglycemic DKA:

   • Don't rule out DKA based solely on normal or near-normal blood glucose levels
   • Consider DKA in patients with acidosis and ketosis regardless of glucose level, especially those on SGLT2 inhibitors 2, 3

3. Confusing DKA with Starvation Ketosis:

   • In starvation ketosis, serum bicarbonate is usually not lower than 18 mEq/L 1

By following these diagnostic criteria and considering potential pitfalls, clinicians can accurately diagnose DKA and initiate appropriate treatment promptly.