What tests are needed to rule out Diabetic Ketoacidosis (DKA)?

Diagnostic Testing for Diabetic Ketoacidosis (DKA)

The diagnosis of DKA requires measurement of blood glucose, blood β-hydroxybutyrate (bOHB), venous pH, serum bicarbonate, and calculation of anion gap. 1

Essential Laboratory Tests for DKA Diagnosis

• Blood glucose measurement - Traditional diagnostic criteria include glucose >250 mg/dL, though euglycemic DKA can occur (especially with SGLT2 inhibitor use) 2
• Blood β-hydroxybutyrate (bOHB) - Specific measurement in blood is the preferred method for diagnosis of DKA 1
• Venous pH - Value <7.3 is diagnostic for DKA 1, 3
• Serum bicarbonate - Value <18 mEq/L is diagnostic for DKA 1, 3
• Anion gap calculation - Elevated anion gap >10 mEq/L supports DKA diagnosis 2
• Serum electrolytes - Needed to calculate anion gap and assess electrolyte imbalances 1, 3

Advantages of Blood β-hydroxybutyrate Testing

• Blood bOHB testing is more accurate than urine ketone testing as bOHB is the predominant ketone body in DKA 1
• Point-of-care blood bOHB testing has high sensitivity (98%) and specificity (85%) for DKA diagnosis 4
• Blood bOHB measurement can detect ketosis earlier than traditional nitroprusside methods that only measure acetoacetate and acetone 1

Limitations of Urine Ketone Testing

• While urine ketones have high negative predictive value (useful for ruling out DKA), they have limitations 1:
  • Nitroprusside method only measures acetoacetate and acetone, not bOHB 1
  • During DKA treatment, bOHB converts to acetoacetate, potentially giving false impression that ketosis is worsening 1
  • Cannot accurately quantify the degree of ketosis 1

Additional Tests to Consider

• Blood urea nitrogen (BUN) and creatinine - To assess renal function and dehydration 1, 2
• Complete blood count - To evaluate for infection or other complications 2
• Serum osmolality - To differentiate DKA from hyperosmolar hyperglycemic state 5
• Electrocardiogram - To assess for cardiac complications 2

Monitoring During Treatment

• Blood glucose, electrolytes, BUN, creatinine, venous pH, and anion gap should be monitored every 2-4 hours during treatment 1, 3
• Blood bOHB is the preferred method for monitoring ketosis resolution during treatment 1, 3
• Venous pH and anion gap can be followed to monitor resolution of acidosis 1

Diagnostic Criteria for DKA Resolution

• Glucose <200 mg/dL 3
• Serum bicarbonate ≥18 mEq/L 3
• Venous pH >7.3 3
• Anion gap ≤12 mEq/L 3

Clinical Pearls

• Blood bOHB testing is superior to urine ketone testing for both diagnosis and monitoring of DKA 1
• Nitroprusside-based blood ketone tests should not be used to monitor treatment of DKA as they can be misleading 1
• Euglycemic DKA (glucose <200 mg/dL) can occur, particularly in patients using SGLT2 inhibitors, during pregnancy, or after insulin administration 6, 2
• Point-of-care bOHB testing at triage can expedite diagnosis and treatment of DKA 4