and 46 in bottom housing portion 32 opposite ends of base member 11 of test strip 10 are gripped and tensioned by bottom housing portion 32 and top housing portion 39 to ensure proper alignment molded pressure pads 35 which are located just inside the cavities on the arms of the cassette provide a specific amount of pressure to the test strip so that it performs as desired these can be changed depending on the stack up or thickness of the particular type of assay conventional porous membrane or macro fluidic channel cover layer 24 is placed over the top of the test strip to ensure that the device is sealed and protected a pressure on the test strip is formed when top housing portion 39 of the cassette is assembled with the bottom housing portion the amount of pressure is one factor affecting the rate of fluid flow through the strip in this embodiment a desiccant not shown may optionally be placed within the cassette web structure under top 39 thereby improving the storability of the assay device cassette 30 may be formed of any suitable rigid material such as plastic or the like in a preferred embodiment as shown in fig1 additional strength to the cassette is provided by web structure 33 other structural shapes may be employed in addition although the c shaped expanse is shown indicated by reference numeral 31 it is contemplated herein that any other shape is within the scope of the invention as long as that shape allows the detector to access the.