A method carried out by a system configured to analyze platelet aggregation includes retaining a ferromagnetic object at an elevation of a chamber in which a sample of blood or plasma is disposed. The ferromagnetic object is retained at the elevation for a period of time. The ferromagnetic object is then released from the elevation. The ferromagnetic object minimal position is measured following the release of the ferromagnetic object. The object minimal position may be correlated with amount of platelet aggregation in the sample.