The present invention relates to a method and to a device for separating plasma from whole blood. The method and device utilize a permeable non-glass fiber matrix containing a polyol which is capable of clumping red blood cells. The matrix, in the absence of such a polyol, would otherwise be porous to red blood cells. The polyol-containing matrix has a first surface and a second surface such that a whole blood sample which is applied to the first surface flows directionally toward the second surface. Plasma separated from whole blood becomes available at the second surface of the matrix and can be tested for the presence of a particular analyte, such as glucose or fructosamine, as provided by multi-layer test devices of the present invention.