An electrochemical test device for determining a concentration of one or more analytes in a fluid sample is provided. The electrochemical test device comprises a set of electrodes including two or more working electrodes, each working electrode for determining the concentration of a corresponding analyte, and sensing chemistry for each working electrode, wherein the sensing chemistry for a first of the two or more working electrodes comprises a diaphorase, an electron transfer agent, an NAD(P)+-dependent dehydrogenase and a cofactor for the NAD(P)+-dependent dehydrogenase, wherein at least some of the diaphorase for the first working electrode is disposed in a diaphorase-containing layer which extends over the first working electrode and at least a second of the two or more working electrodes.