A system for performing multiple assays on a biological sample, comprising: an analyzer comprising: a cartridge port for mating with a test cartridge, a multi-terminal connector comprising a plurality of pins, a processor, a memory coupled to the processor, and universal channel circuitry, wherein the universal channel circuitry comprises a first channel comprising first circuitry comprising one or more switches, and a second channel comprising second circuitry comprising one or more switches; a first test cartridge comprising a light emitter connected to a first contact and a light detector connected to a second contact; and a second test cartridge comprising an amperometric electrode connected to a third contact and a reference electrode connected to a fourth contact, wherein the first contact is electrically connectable to a first pin of the multi-terminal connector, and the second contact is electrically connectable to a second pin of the multi-terminal connector; wherein the third contact is electrically connectable to the first pin of the multi-terminal connector, and the fourth contact is electrically connectable to the second pin of the multi-terminal connector; wherein the first pin is electrically connectable to the first channel, and the second pin is electrically connectable to the second channel; wherein when the first test cartridge is inserted into the cartridge port of the analyzer, the one or more switches of the first circuitry are arranged such that the first channel is configured in a current driver mode, and the one or more switches of the second circuitry are arranged such that the second channel is configured in a current measurement mode; and wherein when the second test cartridge is inserted into the cartridge port of the analyzer, the one or more switches of the first circuitry are arranged such that the first channel is configured in an amperometric measurement mode, and the one or more switches of the second circuitry are arranged such that the second channel is configured in a reference measurement mode. a first test cartridge comprising a light emitter connected to a first contact and a light detector connected to a second contact; and a second test cartridge comprising an amperometric electrode connected to a third contact and a reference electrode connected to a fourth contact, wherein the first contact is electrically connectable to a first pin of the multi-terminal connector, and the second contact is electrically connectable to a second pin of the multi-terminal connector; wherein the third contact is electrically connectable to the first pin of the multi-terminal connector, and the fourth contact is electrically connectable to the second pin of the multi-terminal connector; wherein the first pin is electrically connectable to the first channel, and the second pin is electrically connectable to the second channel; wherein when the first test cartridge is inserted into the cartridge port of the analyzer, the one or more switches of the first circuitry are arranged such that the first channel is configured in a current driver mode, and the one or more switches of the second circuitry are arranged such that the second channel is configured in a current measurement mode; and wherein when the second test cartridge is inserted into the cartridge port of the analyzer, the one or more switches of the first circuitry are arranged such that the first channel is configured in an amperometric measurement mode, and the one or more switches of the second circuitry are arranged such that the second channel is configured in a reference measurement mode.