A diagnostic system is provided herein that includes an instrument comprising an electrochemiluminescence (ECL) detector, and a cartridge configured to fit within a portion of the instrument, wherein the cartridge includes at least one reagent including an ECL label and a blood collection holder. Also provided herein is a system that includes a diagnostic instrument, which includes a pump, an ECL detector, an incubator, a magnet, and an output device, and a cartridge configured to fit within a portion of the diagnostic instrument, a sample holder configured to fit within the cartridge, and a closed fluidic loop between the diagnostic instrument and the cartridge when the cartridge is fit within a portion of the diagnostic instrument, wherein the cartridge is configured to accept a sample from the sample holder and place the sample in fluidic communication with the diagnostic instrument via the closed fluidic loop.