This invention relates to a cartridge for an immunoassay test. The cartridge comprises (a) a probe well comprising a probe and a cap, the cap being in a closed position to enclose the probe in the probe well, wherein the probe has a bottom tip coated with analyte-binding molecules; (b) a sample well to receive a sample; (c) one or more reagent wells; (d) a plurality of wash wells each containing a first aqueous solution; and (e) a measurement well having a light transmissive bottom, the measurement well containing a second aqueous solution; wherein the openings of the sample well, reagent well, measurement well and wash wells are sealed. The present invention also relates to an apparatus for loading and releasing a probe. The apparatus comprises a push pin and a groove to load and transfer the probe to a plurality of locations, such as different wells in the above-mentioned cartridge, to conduct the immunoassay test.