Devices and methods for plasma separation and metering

A sample device for separation of plasma from a patient's liquid test sample for the performance of at least one diagnostic assay, the sample device comprising:

• at least one channel which defines a path for capillary fluid flow and having an opening in an end thereof for drawing the liquid test sample into the sample device;
• at least one cavity in fluidic communication with the at least one channel;
• at least one membrane having an inner surface and an outer surface, wherein the inner surface of the at least one membrane forms at least a portion of at least one side of the at least one cavity, and wherein the at least one membrane has a pore size that substantially prevents agglutinated red blood cells (RBCs) from flowing therethrough;
• at least one reagent positioned within the at least one cavity, wherein the at least one reagent comprises an RBC binding or agglutination material;
• and
• wherein the at least one cavity has a first longitudinal side, a second longitudinal side, a first end side, and a second end side, wherein the at least one membrane is secured to the cavity and positioned and contained between the first end side and the second end side of the cavity, wherein the inner surface of the at least one membrane forms at least a portion of the first or second longitudinal side of the cavity, and wherein the outer surface of the at least one membrane is configured for delivery of plasma therethrough via diffusion upon contact with a solution.