A sample acquiring device for volumetric enumeration of thrombocytes in a blood sample is provided which comprises a measurement cavity for receiving a blood sample. The measurement cavity has a predetermined fixed thickness. The sample acquiring device further comprises a reagent, which is arranged in a dried form on a surface defining the measurement cavity. The reagent comprises a haemolyzing agent for lysing red blood cells in the blood sample, and optionally a staining agent for selectively staining thrombocytes in the blood sample. A system comprises the sample acquiring device and a measurement apparatus. The measurement apparatus comprises a sample acquiring device holder, a light source, and an imaging system for acquiring a digital image of a magnification of the sample. The measurement apparatus further comprises an image analyzer arranged to analyze the acquired digital image for determining the number of thrombocytes in the blood sample.