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Abstract |
Stability of Ketone Bodies in Serum in Dependence on Storage Time and Storage Temperature |
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The serum concentrations of β-hydrorybutyrate and acetoacetate as well as the β-hydrorybutyrate/acetoacetate ratio are important parameters for the differential diagnosis of certain inborn errors of metabolism. Acetoacetate, however, is an unstable compound which becomes rapidly decarboxylated. At a storage temperature of -20°C about 40% of the acetoacetate is lost within 7 days and after 40 days storage at this temperature virtually all of the acetoacetate has become degraded. At -80°C the decomposition of acetoacetate occurs with a much slower rate and only 15% of the initial acetoacetate is lost after 40 days storage. The rate constants for the decarboxylation reaction were found to be (6.4 ± 2.9) * 10-5 [min-1] at -20°C and (04 ± 0.3) * 10-5 [min-1] at -80°C. In contrast, β-hydroxybutyrate is very stable during storage and hence should be used as main parameter for the evaluation of ketonemia. If determination of acetoacetate and/or of the β-hydroxybutyrate/acetoacetate ratio is necessary, an assay immediately after collecting the serum samples is recommended. Otherwise, the serum samples should be frozen as soon as possible and stored at -80°C during transport and storage. |
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