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

Diagnostic Criteria for Diabetic Ketoacidosis (DKA)

The diagnostic criteria for diabetic ketoacidosis (DKA) include blood glucose >250 mg/dL, venous pH <7.3, serum bicarbonate <15 mEq/L, and moderate ketonuria or ketonemia. 1, 2

Core Diagnostic Parameters

• Blood glucose >250 mg/dL: Hyperglycemia is a fundamental component of classic DKA diagnosis 1
• Venous pH <7.3: Acidosis is required for diagnosis and reflects the severity of ketoacidosis 1, 2
• Serum bicarbonate <15 mEq/L: Low bicarbonate indicates metabolic acidosis 1, 2
• Presence of ketones: Either moderate ketonuria or ketonemia must be present 1
• Anion gap >12 mEq/L: Reflects the metabolic acidosis from ketone accumulation 2

Laboratory Evaluation

• Obtain complete metabolic panel, venous blood gases, complete blood count, urinalysis, and serum ketones immediately upon presentation 1
• Calculate anion gap = [Na⁺] - ([Cl⁻] + [HCO₃⁻]) to assess severity of metabolic acidosis 2
• Correct serum sodium for hyperglycemia using formula: [measured Na (mEq/L)] + [glucose (mg/dL) - 100]/100 × 1.6 1
• Direct measurement of β-hydroxybutyrate (β-OHB) in blood is preferred over nitroprusside method (which only measures acetoacetic acid and acetone) 2

Special Considerations

Euglycemic DKA

• A variant of DKA where blood glucose is <250 mg/dL but other criteria (acidosis, ketosis) are present 3
• Most commonly occurs with SGLT2 inhibitor use, pregnancy, starvation, alcohol use, or chronic liver disease 3
• Requires the same aggressive treatment approach as classic DKA 4

Severity Classification

• Mild DKA: Venous pH 7.25-7.30, bicarbonate 15-18 mEq/L, alert mental status 1
• Moderate DKA: Venous pH 7.00-7.24, bicarbonate 10-15 mEq/L, drowsy mental status 1
• Severe DKA: Venous pH <7.00, bicarbonate <10 mEq/L, stupor/coma 5

Monitoring During Treatment

• Blood should be drawn every 2-4 hours to measure electrolytes, glucose, BUN, creatinine, osmolality, and venous pH 2
• Venous pH (typically 0.03 units lower than arterial pH) and anion gap can be followed to monitor resolution of acidosis 2
• Ketonemia typically takes longer to clear than hyperglycemia, requiring continued monitoring 2

Resolution Criteria

• Glucose <200 mg/dL 2
• Serum bicarbonate ≥18 mEq/L 2
• Venous pH >7.3 2
• Anion gap ≤12 mEq/L 2

Common Pitfalls to Avoid

• Relying solely on urine ketones for diagnosis or monitoring response to treatment, as the nitroprusside method doesn't measure β-OHB 2
• Failing to recognize euglycemic DKA when blood glucose is <250 mg/dL 3
• Discontinuing insulin therapy prematurely before ketoacidosis resolves 6
• Inadequate monitoring of electrolytes, particularly potassium, during treatment 6

By systematically evaluating these parameters, clinicians can accurately diagnose DKA and monitor treatment response to reduce morbidity and mortality associated with this serious metabolic emergency.