The ratio of the ketone bodies acetoacetic acid and beta-hydroxybutyric acid reflect the metabolic status of the patient, especially in patients with liver disease. Changes in the ketone body ratio may indicate a patient at risk for liver failure or other complications.
Specimen: The specimen should be collected on ice-water (a slurry of ice and water). If the sample cannot be analyzed immediately, then it should be frozen immediately. Some papers specify an arterial blood sample.
ketone body ratio =
= (acetoacetic acid in µmol/L) / (hydroxybutyric acid in µmol/L)
Alternatively, the ratio may have the acetoacetic and hydroxybutyric acid may be reversed as numerator and denominator.
Interpretation:
• As a person develops ketosis and deteriorating liver function, the ketones, especially beta-hydroxybutyric acid, increase, with lowering of the ratio.
• The ratio conveying significance varies with different studies and different patient populations.
• The duration of the decline in the ratio is important in distinguishing transient complications from more serious ones. A decline for several days that does not return to normal is more ominous than a transient decline.
• In patients with hepatitis, a decline in the ketone body ratio in conjunction with development of a coagulopathy may precede development of fulminant hepatitis. Saibara et al (1992) used a ratio < 0.6 for 4 or more days as significant for patients with acute hepatitis. Saibara et al reported a ratio < 0.4 1-2 days after admission was seen in nonsurvivors.
• A decrease in the ketone body ratio in a liver transplant patient may reflect transplant failure.
• Patients who show a decline in the ketone body ratio after surgery tend to have more complications. If the decline is prolonged without a return to normal, then the complications may be serious with multi-organ failure.
• Asano et al used a ratio < 0.4 that did not increase as indicating risk for multiorgan failure in patients after hepatectomy.
