The POC blood ketone test meter measures the ketone 3-beta-hydroxybutyrate (beta-OHB) in the blood of patients with diabetes. In comparison to the standard laboratory enzymatic method the ketone sensor accurately measured beta-OHB concentrations in patients with DKA (limits of agreement [LOA] 0.9 to 1.0 mmol/l) or starvation-induced ketonaemia (LOA-0.5 to +0.5 mmol/l).7
In an emergency department (ED) study of 173 hyperglycaemic patients, POC blood ketone tests were compared to urine dipstick analysis.8 Several cut-off points were evaluated. At a beta-OHB value <3 mmol/l or ketonuria ≤1+, ketoacidosis could be excluded (negative predictive value 100%). At 2+ cut-off points for ketonuria and at the 3 mmol/l cut-off point for ketonaemia the two tests had the same sensitivity (100%), but the specificity of beta-OHB (94%) was significantly higher (P<0.001) than that of ketonuria (77%). Overall the study showed that measurement of beta-OHB in capillary blood was faster and more effective than the use of urine dipsticks to detect ketoacidosis. A follow-up study by the same group on the correlation between urine and capillary blood ketones showed a good correlation for low values, but a poor correlation for high values. The study concluded that either test could be used to exclude ketosis, but that the capillary blood ketone test is more accurate to confirm ketoacidosis.9
A prospective observational study in an ED comparing ketone dipstick testing with capillary blood ketone testing, showed that the positive likelihood ratio (LR+) for DKA was 3 using urine ketone dipstick testing, and 4 for capillary blood ketone testing. In determining hyperketonaemia (both in diabetic ketosis and diabetic ketoacidosis) the LR+was 1.8 and 2, respectively.10
What this technology adds
Point-of-care blood tests for ketones allow for rapid and accurate diagnosis and monitoring of diabetic ketoacidosis. A clear role of the ketone blood test in primary care is as yet uncertain; however, it may be useful in the assessment of a patient with known diabetes who is unwell, and/or has very high glucose levels.
A study in an ED setting compared the results of this POC with standard clinical criteria for predicting DKA11 in 160 patients presenting with blood glucose levels of >6.4 mmol/l. The study concluded that the POC test for beta-OHB was as sensitive as more established indicators of DKA and more useful than glucose alone.
Another study investigated the performance of the POC blood ketone test in the diagnosis of DKA in 450 patients with type 2 diabetes in the ED. DKA was diagnosed in 50 of these patients, with capillary ketonaemia (beta-OHB >3.0 mmol/L) providing the best accuracy for the diagnosis of DKA, compared with serum ketonaemia or ketonuria.12
