Table 2.

Enzymatic and electrochemical reactions in POC testing devices for ketones and lactate. ∗Predominant ketone present in patients with diabetic ketoacidosis. β-HB, beta-hydroxybutyrate.

Substance	Enzyme	Enzymatic reaction	Electrochemical reaction
Lactate	Lactate oxidase	$\mathrm{L}\mathrm{a}\mathrm{c}\mathrm{t}\mathrm{a}\mathrm{t}\mathrm{e}+{\mathrm{O}}_2\rightleftharpoons \mathrm{p}\mathrm{y}\mathrm{r}\mathrm{u}\mathrm{v}\mathrm{a}\mathrm{t}\mathrm{e}+{\mathrm{H}}_2{\mathrm{O}}_2$	${\mathrm{H}}_2{\mathrm{O}}_2\rightleftharpoons {\mathrm{O}}_2+2{\mathrm{H}}^{+}+2{\mathrm{e}}^{–}$
Lactate	Lactate dehydrogenase	$\mathrm{L}\mathrm{a}\mathrm{c}\mathrm{t}\mathrm{a}\mathrm{t}\mathrm{e}+\mathrm{N}\mathrm{A}{\mathrm{D}}^{+}\rightleftharpoons \mathrm{p}\mathrm{y}\mathrm{r}\mathrm{u}\mathrm{v}\mathrm{a}\mathrm{t}\mathrm{e}+\mathrm{N}\mathrm{A}\mathrm{D}\mathrm{H}+{\mathrm{H}}^{+}$	$\mathrm{N}\mathrm{A}\mathrm{D}\mathrm{H}\rightleftharpoons \mathrm{N}\mathrm{A}{\mathrm{D}}^{+}+{\mathrm{H}}^{+}+2{\mathrm{e}}^{–}$
β-HB∗	β-HB dehydrogenase	$\mathrm{\beta }-\mathrm{H}\mathrm{B}+\mathrm{N}\mathrm{A}{\mathrm{D}}^{+}\rightleftharpoons \mathrm{a}\mathrm{c}\mathrm{e}\mathrm{t}\mathrm{o}\mathrm{a}\mathrm{c}\mathrm{e}\mathrm{t}\mathrm{a}\mathrm{t}\mathrm{e}+\mathrm{N}\mathrm{A}\mathrm{D}\mathrm{H}+{\mathrm{H}}^{+}$	$\mathrm{N}\mathrm{A}\mathrm{D}\mathrm{H}\rightleftharpoons \mathrm{N}\mathrm{A}{\mathrm{D}}^{+}+{\mathrm{H}}^{+}+2{\mathrm{e}}^{–}$