What lab test is used to diagnose Hyperosymmetric Hyperglycemic Syndrome (HHS) in a patient?

From the Guidelines

To diagnose Hyperosmolar Hyperglycemic Syndrome (HHS) in a patient, the most critical laboratory tests include serum glucose, serum osmolality, electrolytes, blood urea nitrogen (BUN), creatinine, and arterial blood gases, with a particular focus on serum glucose levels above 600 mg/dL and effective serum osmolality above 320 mOsm/kg, as indicated by 1 and 1. When evaluating a patient for HHS, it is essential to consider the diagnostic criteria outlined in the evidence, which includes severe hyperglycemia, hyperosmolality, and the absence of significant ketosis.

• The calculation of effective serum osmolality using the formula: 2[measured Na (mEq/l)] + glucose (mg/dl)/18, as mentioned in 1, is crucial for diagnosis.
• A comprehensive metabolic panel should be ordered to assess glucose levels, kidney function, and electrolyte abnormalities, particularly sodium, potassium, and phosphate, as these are critical in managing HHS.
• Additionally, a complete blood count, urinalysis (which typically shows minimal or no ketones in HHS), and arterial blood gases (to assess acid-base status) should be performed to differentiate HHS from other conditions like diabetic ketoacidosis (DKA), as noted in 1.
• The distinction between HHS and DKA is vital, with HHS characterized by minimal ketosis and acidosis, typically with a pH above 7.3, as highlighted in 1 and 1. These tests are critical because HHS has a high mortality rate and requires prompt diagnosis and treatment with fluid resuscitation and insulin therapy, emphasizing the need for rapid and accurate diagnosis to improve patient outcomes.

From the Research

Diagnosis of Hyperosmolar Hyperglycaemic Syndrome (HHS)

To diagnose HHS, several lab tests are used, including:

• Measurement of serum osmolality, which is calculated using the formula: [(2×Na+) + glucose + urea] 2, 3
• Blood glucose levels, with HHS typically characterized by marked hyperglycaemia ≥30 mmol/L 2
• Venous pH, with HHS characterized by a pH > 7.3 2
• Bicarbonate levels, with HHS characterized by bicarbonate ≥15 mmol/L 2
• Ketone levels, with HHS characterized by slight ketonuria or ketonaemia ≤3.0 mmol/L 2, 4
• Electrolyte panels, including sodium, potassium, and other electrolytes 2, 5, 6
• Calculation of plasma osmolality, with HHS characterized by osmolality ≥320 mOsm/kg 2, 3, 4

Key Diagnostic Criteria

The key diagnostic criteria for HHS include:

• Plasma glucose > 600 mg/dl 4
• Venous pH > 7.25 4
• Sodium bicarbonate > 15 mmol/l 4
• Slight ketonuria or ketonaemia ≤3.0 mmol/L 2, 4
• Plasma osmolality > 320 mOsm/kg 2, 3, 4
• Impairment of consciousness, such as aggression, unconsciousness, or convulsions 4