A fluidic medical diagnostic device permits measurement of analyte concentration or a property of a biological fluid, particularly the coagulation time of blood. The device has at one end a sample port for introducing a sample and at the other end a bladder for drawing the sample to a measurement area. A channel carries the sample from the sample port to the measurement area, and a stop junction, between the measurement area and bladder, halts the sample flow. The desired measurement can be made by placing the device into a meter which measures a physical property of the sample—typically, optical transmittance—after it has interacted with a reagent in the measurement area.