A diagnostic device is provided that comprises a light source for transmitting a light beam through a blood sample to a light detector, and a permanent magnet, wherein one of the permanent magnet and blood sample is automatically movable relative to the other between a “HIGH” magnetic state position and a “LOW” magnetic state position, such that a substantially high magnetic field is applied to the blood sample causing any hemozoin in the blood sample to tend toward perpendicular orientation to the substantially magnetic field and the suppression, or enhancement of light based on its polarization, and a zero-to-near-zero magnetic field is applied to the blood sample causing the randomization of any hemozoin in the blood sample and a baseline amount of light to pass through the blood sample in the “LOW” magnetic state position.