A microfluidic detection system for detection of target entities of micrometer size in a fluid containing a quantity of magnetic beads and a quantity of target entities bound to one or more magnetic beads, in which each target entity bound to a magnetic bead has a smallest effective dimension greater than a largest effective dimension of each magnetic bead, the system comprising: a detector component including: a body defining a reservoir; a plate disposed within said reservoir and separating said reservoir into a first chamber and a second chamber, said plate defining a plurality of openings therethrough, each opening having an effective dimension sized to always permit passage of the largest effective dimension of each magnetic bead and further sized to always prevent passage of the smallest effective dimension of each target entity; said first chamber of said reservoir having a first inlet and a first outlet, said first inlet fluidly connectable to a source of the fluid containing the target entities; and a magnet disposed relative to said reservoir so that said second chamber of said reservoir and said plate are situated between said magnet and said first chamber of said reservoir, said magnet configured to generate a magnetic force sufficient to attract magnetic beads in said first chamber of said reservoir to said second chamber of said reservoir; and a pump (40; 41) for continuously flowing the fluid from the source of the fluid containing the target entities through said first chamber of said reservoir. a detector component including: a body defining a reservoir; a plate disposed within said reservoir and separating said reservoir into a first chamber and a second chamber, said plate defining a plurality of openings therethrough, each opening having an effective dimension sized to always permit passage of the largest effective dimension of each magnetic bead and further sized to always prevent passage of the smallest effective dimension of each target entity; said first chamber of said reservoir having a first inlet and a first outlet, said first inlet fluidly connectable to a source of the fluid containing the target entities; and a magnet disposed relative to said reservoir so that said second chamber of said reservoir and said plate are situated between said magnet and said first chamber of said reservoir, said magnet configured to generate a magnetic force sufficient to attract magnetic beads in said first chamber of said reservoir to said second chamber of said reservoir; and a body defining a reservoir; a plate disposed within said reservoir and separating said reservoir into a first chamber and a second chamber, said plate defining a plurality of openings therethrough, each opening having an effective dimension sized to always permit passage of the largest effective dimension of each magnetic bead and further sized to always prevent passage of the smallest effective dimension of each target entity; said first chamber of said reservoir having a first inlet and a first outlet, said first inlet fluidly connectable to a source of the fluid containing the target entities; and a magnet disposed relative to said reservoir so that said second chamber of said reservoir and said plate are situated between said magnet and said first chamber of said reservoir, said magnet configured to generate a magnetic force sufficient to attract magnetic beads in said first chamber of said reservoir to said second chamber of said reservoir; and a pump (40; 41) for continuously flowing the fluid from the source of the fluid containing the target entities through said first chamber of said reservoir.