1. A diagnostic test system, comprising: a housing comprising a port for receiving a test strip that supports lateral flow of a fluid sample along a lateral flow direction and comprises a labeling zone containing a labeling substance that binds a label to a target analyte and a detection zone comprising at least one test region containing an immobilized substance that binds the target analyte, wherein the detection zone includes an area that is exposed for optical inspection and is characterized by a first dimension transverse to the lateral flow direction and a second dimension parallel to the lateral flow direction; a reader configured to obtain separable light intensity measurements from localized regions of the exposed area of the detection zone when the test strip is loaded in the port, wherein each of the localized regions is characterized by at least one surface dimension smaller than the first dimension; and a data analyzer operable to identify ones of the light intensity measurements obtained from the at least one test region and to compute at least one parameter from the identified ones of the light intensity measurements.