Systems, combinations, and/or methods for separating plasma from a drop of blood use a capillary tube and a filter membrane having a rough side and a smooth side. The pores on the rough side of the filter membrane are large enough for blood cells to enter and be captured. The pores on the smooth side of the filter membrane are small enough to block blood cells, but allow the plasma within the drop of blood to pass through the smooth side of the filter membrane.
