Blood filter device

A blood filter device comprising a tubular housing and a filtration section wherein the filtration portion along a tubular portion is movable with a tubular housing volume, the filtration portion is sealed movable through the tubular housing and the tubular housing volume to a variable first tubular housing volume and a variable second tubular enclosure volume separating, so that blood flows during movement of the filtration portion in the first tubular casing volume through the first passageway to the unfiltered side out, whereby a blood plasma / serum can pass through the filter medium and the residual blood flows through the second communication path in the variable second tubular housing volume.