A medical system for determining an analyte quantity in a blood sample via a cartridge that spins around a rotational axis. The cartridge may include: a separation chamber that separates blood plasma from the sample; a processing chamber containing a reagent with a specific binding partner which binds to the analyte to form an analyte specific binding partner complex; a first valve structure connecting the separation chamber to the processing chamber; a measurement structure to measure the quantity of the analyte, wherein the measurement structure includes a chromatographic membrane with an immobilized binding partner for direct or indirect binding of the analyte or the analyte specific binding partner complex, and an absorbent structure that is nearer to the axis than the membrane; a second valve structure connecting the processing chamber to the measurement structure; and a fluid chamber filled with a washing buffer and fluidically connected to the measurement structure.