Ketone Bodies in Diabetes Mellitus
المؤلف:
Marcello Ciaccio
المصدر:
Clinical and Laboratory Medicine Textbook 2021
الجزء والصفحة:
p404-405
2025-11-03
55
Measurement of blood (ketonemia) or urine (ketonuria) concentrations of ketone bodies (acetone, acetoacetate, and d-β- hydroxybutyrate) is recommended to aid in the diagnosis of diabetic ketoacidosis in patients with type 1 diabetes and gestational diabetes. Indeed, the presence of ketones may indicate the onset of ketoacidosis, a condition that requires immediate medical action. In the patient with this condition, the increased concentration of ketone bodies leads to a lowering of the blood pH, resulting in acidosis (arterial pH <7.3 and/or HCO-3 levels <15 mEq/L).
Under normal conditions and with a balanced diet, ketone bodies are produced in small amounts because acetyl-CoA is mainly used in the citric acid cycle. Conversely, under conditions (e.g., diabetes and prolonged fasting) that lead to accumulation of acetyl-CoA (as a result of increased gluconeogenesis in the liver and fatty acid oxidation in muscle and liver), the liver gets rid of excess fatty acids by producing ketone bodies, which it sends through the bloodstream to peripheral tissues where they are oxidized to produce energy (hydroxybutyrate).
The symptoms that characterize diabetic ketoacidosis are fatigue, general malaise, polyuria, polydipsia, cardiac arrhythmias, drowsiness, weight loss, and bradypnea. Other signs that appear are dehydration, hypotension, ECG abnormalities, brain dysfunction, loss of muscle mass, and Kussmaul’s breath.
The concentration of ketone bodies can be measured both in plasma and in urine. However, we must emphasize that ketonuria does not express exactly the level of ketone mia in real time, but it provides indirect information about it, with a delay proportionate to the length of the interval between emptying the bladder and the other. Moreover, it does not detect the presence of all three ketone bodies but only of acetoacetate since β-hydroxybutyrate is not detect able by standard sticks, and acetone is eliminated by breath.
Preanalytical Aspects
Because acetone is volatile and acetic acid may be an energy source for bacteria, the analysis of fresh urine samples is recommended.
Increased levels of ketone bodies may be present in healthy subjects during fasting and in the morning urine of 30% of pregnant women.
Analytical Aspects
Urinary tests determine the presence of acetoacetate (which accounts for 10–25% of the total ketone bodies) using a colorimetric reaction with sodium nitroprusside. At alkaline pH, sodium nitroprusside reacts with acetone and acetoacetic acid (a product of acetone), forming a complex that results in color development. It is susceptible to acetoacetic acid and does not react with more complex ketone bodies.
False positives (in the case of the intake of drugs based on sulfhydryl compounds such as captopril, acetylcysteine, and penicillamine) and false negatives may occur, the latter related to an excess of vitamin C, excessive intake of liquids that can dilute the urine, and the degradation of the test strips over time.
In recent years, POCT methods have been developed for determining ketone bodies in capillary blood. These instruments measure β-hydroxybutyrate, which represents the pre dominant and earliest-appearing ketone.
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