When should beta hydroxybutyrate (BHB) be checked in patients with diabetes?

When to Check Beta-Hydroxybutyrate in Patients with Diabetes

Beta-hydroxybutyrate (BHB) should be measured in individuals who are prone to ketosis (those with type 1 diabetes, history of diabetic ketoacidosis, or treated with SGLT2 inhibitors) when they have unexplained hyperglycemia or symptoms of ketosis (abdominal pain, nausea), and should be specifically used for diagnosis and monitoring of diabetic ketoacidosis (DKA). 1

Primary Indications for BHB Testing

1. For Diagnosis of DKA:

   • In patients presenting with hyperglycemia (typically >250 mg/dL)
   • When symptoms suggestive of DKA are present (nausea, vomiting, abdominal pain, Kussmaul respirations, dehydration, altered mental status) 1
   • A BHB value ≥3.0 mmol/L in children and ≥3.8 mmol/L in adults with uncontrolled diabetes can be used to diagnose DKA 2

2. For Monitoring During DKA Treatment:

   • BHB should be used for monitoring the treatment of DKA 1
   • DKA resolution can be defined as plasma BHB <1.5 mmol/L 3
   • Note: Blood ketone determinations that rely on the nitroprusside reaction should NOT be used to monitor treatment of DKA 1

3. For High-Risk Patients:

   • Patients with type 1 diabetes
   • Patients with a history of DKA
   • Patients treated with SGLT2 inhibitors
   • When these high-risk patients experience:
     • Unexplained hyperglycemia
     • Symptoms of ketosis (abdominal pain, nausea) 1

Clinical Decision Points for BHB Testing

Screening for DKA

• A capillary BHB level >3.1 mmol/L has 100% sensitivity and 96% specificity for diagnosing DKA in patients with severe hyperglycemia 4
• For screening purposes, a BHB cutoff of 0.66 mmol/L has 95% sensitivity and 89.2% specificity, with a negative predictive value of 99.9% 5

Diagnostic Thresholds

• BHB ≥1.0 mmol/L can accurately predict DK/DKA (sensitivity 85.1%, specificity 95.3%) 5
• BHB correlates more strongly with anion gap (r=0.75) than with serum bicarbonate (r=-0.69) 6

Advantages of BHB Testing Over Traditional Methods

1. Superior to Urine Ketone Testing:

   • Serum BHB turns negative earlier than urine ketones during recovery 5
   • Urine glucose testing is not recommended for routine care of patients with diabetes 1

2. More Specific Than Traditional DKA Criteria:

   • BHB directly measures the predominant ketone body in DKA
   • There is marked variability in the relationship between BHB and bicarbonate due to other acid-base disturbances 2

Implementation in Clinical Practice

• Patients at risk for ketosis should be educated about when to check BHB and implement sick-day rules when levels are elevated 1
• For patients with newly diagnosed type 2 diabetes, BHB testing is not routinely required unless symptoms suggest possible DKA 1
• BHB testing should be incorporated into sick-day protocols for high-risk patients

Common Pitfalls and Caveats

1. Reliance on Urine Ketones Alone:

   • Urine ketones may remain positive even after DKA resolves
   • Urine ketones measure acetoacetate, not BHB (the predominant ketone in DKA)

2. Misinterpretation of Results:

   • BHB levels should be interpreted in the context of clinical presentation and other laboratory values
   • A normal BHB (<0.66 mmol/L) effectively rules out DKA (99.9% negative predictive value) 5

3. Testing Method Limitations:

   • Only FDA-approved devices with proven accuracy should be used 1
   • Test strips should be unexpired and properly stored

By following these guidelines for BHB testing, clinicians can more accurately diagnose and monitor DKA, potentially improving outcomes for patients with diabetes at risk for this serious complication.