A flow-through assay device for detecting the presence or quantity of an
analyte residing in a test sample is provided. The device utilizes a
scavenging zone that contains a capture reagent for the analyte of
interest. The capture reagent may capture a quantity of the analyte that
is less than or equal to a predefined base quantity of the analyte, such
as a quantity considered "normal" for a particular test sample. Thus, the
capture reagent is able to prevent some of the analyte from being
detected. In this manner, the sensitivity of the assay device may be
reduced in a simple, inexpensive, yet effective manner.