A diagnostic device for testing a liquid sample has a carrier for receiving at least a portion of the sample and a sample delivery means. The sample delivery means has a delivery channel that is in fluid communication with the carrier. The delivery channel has a first delivery channel surface facing a second delivery channel surface, wherein the first delivery channel surface is spaced apart from said second delivery channel surface by a distance that promotes longitudinal advancement of the sample along the delivery channel by capillary action. A deposition channel, to promote lateral dispersal of the sample across a corner, is formed either in a housing or between the housing and the carrier.