Acetoacetate 

Updated: Nov 11, 2013
  • Author: Carlos Solano Loran, MD; Chief Editor: Eric B Staros, MD  more...
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Reference Range

The normal reference range for quantitative acetoacetate assays (Gas chromatography) are as follows:

  • Normal range (plasma/serum): 5-30 µg/mL (conventional units)

Semiquantitative methods, although nonspecific for acetoacetate, are frequently used to determine the presence of ketone bodies (acetone and acetoacetate) in urine and blood and are discussed in Ketones.

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Interpretation

Ketone bodies, including acetoacetate, are constantly produced in insignificant amount by the liver.

High levels of acetoacetate in blood might result from the following:

  • Decreased availability of carbohydrates (eg, starvation, alcoholism)
  • Abnormal use of carbohydrates storage (eg, uncontrolled diabetes, glycogen storage diseases)

When the rate of synthesis of acetoacetate and ketone bodies exceeds the rate of utilization, their concentration in blood increases, which is known as ketonemia.

Extreme accumulation of acetoacetate and other ketones can lead to metabolic acidosis, which is defined as ketoacidosis.

Diabetic ketoacidosis and alcoholic ketoacidosis are by far the most common causes of an elevated acetoacetate level and ketosis.

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Collection and Panels

Either for semiquantitative or quantitative assessments, the collection details are as follows:

  • Collection method: Venipuncture
  • Specimen type: Plasma or serum
  • Specimen volume: 3 mL (ideal volume)/1.2 mL (minimum volume)
  • Container: For plasma, draw blood in a lavender (EDTA) or pink-top tube [1] and centrifugate to yield 3 mL of plasma; for serum, draw blood in a red-top tube [1] and centrifugate to yield 3 mL of serum
  • Keep refrigerated or frozen (preferred) up to 4 days
  • Reject heparinized or warm specimens
  • Hemolyzed, lipemic, or icteric specimens might be accepted

The underlying metabolic mechanism behind elevated acetoacetate levels might be further assessed by the following related tests:

  • Blood glucose value
  • Metabolic panel
  • Renal function studies
  • Arterial blood gases testing
  • Urine ketones value
  • Serum β-hydroxybutyrate value
  • Serum osmolality
  • Serum bicarbonate value
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Background

Description

Acetoacetate, also termed acetoacetic acid, is a weak β-keto acid produced from acetyl-CoA in the mitochondrial matrix of hepatocytes when limited carbohydrate availability stimulates the activation of glucagon and other counter-regulatory hormones in order to promote the oxidation of fatty acids as alternative energy sources. Since acetoacetate and β-hydroxybutyrate are water soluble, they can circulate from the liver to other tissues, where both compounds are reconverted to acetyl-CoA to produce energy through the citric acid cycle.

Under physiologic conditions, only the myocardium uses fatty acids preferentially for energy supply, and most other tissues metabolize glucose to meet their energetic demands. , under ketotic conditions, when the availability of carbohydrates is reduced, the heart and the brain can successfully use ketone bodies as an energy source. [2]

Three days after an individual undergoes a ketogenic insult (eg, starvation, diabetic ketoacidosis, alcoholic ketoacidosis), the brain receives up to 25% of its energy from ketone bodies. This increases to 70% after 4-5 days, [2] which represents the main metabolic contribution of acetoacetate.

Indications/applications

Testing of serum acetoacetate is indicated in the diagnosis of ketoacidosis mainly in suspected diabetic ketoacidosis and alcohol-induced ketoacidosis.

The triad of hyperglycemia, anion gap metabolic acidosis, and ketonemia characterizes diabetic ketoacidosis. [3] Although metabolic acidosis is often the major finding in diabetic ketoacidosis, ketonemia may be challenging to prove. β-hydroxybutyrate, the ketone body predominately elevated in theses cases, levels are laborious and expensive to determine; hence, acetoacetate levels in blood may be used as an indirect reflection of the severity of acidosis, especially in cases of weakly positive semiquantitative determinations.

Alcoholic ketoacidosis represents a clinical syndrome characterized by metabolic acidosis with an elevated anion gap, elevated serum ketone levels, and a normal or low glucose concentration [4] in the setting of excessive alcohol intake. Serum acetoacetate constitutes the most widely available and easily measured ketone body in most hospitals.

Acetoacetate level also plays a role in differentiating insulin-induced hypoglycemia from hypoglycemia secondary to limited carbohydrate intake. Only in the latter, the counter-regulatory catabolic pathways resulting from starvation lead to ketogenesis and high acetoacetate levels.

Considerations

Pregnancy and fasting represent 2 physiological conditions associated with elevated levels of acetoacetate without acidosis and do not necessarily represent evidence of disease.

While not always excreted in proportion to blood ketone concentrations, urine ketones can be used for monitoring of control in patients with diabetes type 1 during acute illness, stress, pregnancy, or persistent hyperglycemia. [5]

Serial measurements of acetoacetate are not clinically useful to assess adequacy of diabetic ketoacidosis treatment. As diabetic ketoacidosis is treated, β-hydroxybutyrate is converted to acetoacetate and ketoacidosis seems to worsen. [5]

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