Processing of dried blood samples on lateral flow paper

A method of processing a sample of blood on a piece of lateral flow paper, comprising:

• disconnecting a paper holder from a paper cover body to expose part of a piece of lateral flow paper held by the paper holder;
• on the exposed part of the lateral flow paper, determining a transition area between a first area with blood cells and a second area substantially without blood cells;
• and
• cutting the piece of lateral flow paper based on the determined transition area to obtain a cut off piece of the lateral flow paper comprising separated blood serum.

A grinder for use in a method of processing a piece of lateral flow paper, comprising:

• a grinder body defining a grinder storage volume with a top opening for accessing the grinder storage volume;
• and
• one or more through holes providing a fluid connection through the grinder body into the grinder storage volume,
• wherein the grinder body further comprises one or more grinding protrusions at an outer surface of the grinder body, which one or more grinding protrusions face away from the grinder storage volume.