A sample device for separating and metering a plasma sample from a patient's liquid test sample, the liquid test sample being a whole blood sample, for the performance of one or more diagnostic assay, comprising: a top portion, the top portion comprising a first end, a second end, a top side, a bottom side, and a sample channel disposed between the top side and bottom side and having a first opening at the second end for collecting a patient's liquid test sample, the sample channel extending longitudinally from the second end to the first end of the top portion, wherein the first end has a second opening; a bottom portion, the bottom portion comprising a first end, a second end, a top side, and a bottom side, wherein the bottom portion is secured to the top portion; at least one red blood cell capture membrane, the at least one red blood cell capture membrane comprising a first end and a second end,; at least one plasma membrane comprising a first end and a second end, wherein the first end of the plasma membrane is in substantially direct contact with the second end of the at least one red blood cell capture membrane and at least a portion of the second opening is open to, in direct contact with, and/or in fluid communication with at least a portion of the red blood cell capture membrane, characterized in that the at least one red blood cell capture membrane is entirely contained between the top portion and bottom portion of the sample device, whereas a portion of the plasma membrane comprising the second end, protrudes from and/or through the first end of the top portion such that the plasma membrane comprises an exposed portion that is not contained within or between the top portion and the bottom portion of the sample device. a top portion, the top portion comprising a first end, a second end, a top side, a bottom side, and a sample channel disposed between the top side and bottom side and having a first opening at the second end for collecting a patient's liquid test sample, the sample channel extending longitudinally from the second end to the first end of the top portion, wherein the first end has a second opening; a bottom portion, the bottom portion comprising a first end, a second end, a top side, and a bottom side, wherein the bottom portion is secured to the top portion; at least one red blood cell capture membrane, the at least one red blood cell capture membrane comprising a first end and a second end,; at least one plasma membrane comprising a first end and a second end, wherein the first end of the plasma membrane is in substantially direct contact with the second end of the at least one red blood cell capture membrane and at least a portion of the second opening is open to, in direct contact with, and/or in fluid communication with at least a portion of the red blood cell capture membrane, characterized in that the at least one red blood cell capture membrane is entirely contained between the top portion and bottom portion of the sample device, whereas a portion of the plasma membrane comprising the second end, protrudes from and/or through the first end of the top portion such that the plasma membrane comprises an exposed portion that is not contained within or between the top portion and the bottom portion of the sample device.