The cardinal biochemical features of diabetic ketoacidosis are hyperketonaemia and metabolic acidosis, in concert with variable hyperglycaemia. While no univerally agreed criteria for diagnosis exist, diabetic ketoacidosis may be defined as in Box 1.1.
Box 1.1 Definition of diabetic ketoacidosis
• Blood total ketone body concentration, i.e. the sum of acetoacetate and 3-hydroxybutyrate > 5 mmol/L.
Note that biochemical confirmation of the diagnosis is often based on semi-quantitative urine dipstick methods, a minority of centres having clinical chemistry laboratories that can measure blood ketone body concentrations. The diagnostic criteria that we use are presented in Box 1.2. Note that no threshold for hyperglycaemia is included in this definition, reflecting the wide variability in blood glucose concentrations.
Box 1.2 Practical biochemical definition of diabetic keto-acidosis
• Blood bicarbonate concentration (capillary or arterial) < 15 mmol/L
• Significant ketosis, defined as urine Ketostix® (Bayer Diagnostics) reaction ++ or plasma Ketostix® + or more).
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