There is provided an assay device comprising a lid and a base, said base comprising, a sample addition zone, a reaction zone and an absorbing zone, said components being in fluid connection and being part of a fluid passage leading from the sample addition zone to the absorbing zone, wherein: (a) a sample addition well is integrated in the lid, (b) the absorbing zone consists of an area on an non-porous substrate, having substantially perpendicular projections, said projections defining a volume, which together with the volume of the fluid passage defines the sample volume subjected to the assay, and (c) at least one filter is between the sample addition well and the sample addition zone. There is further provided methods for handling samples.