The present invention provides a lateral flow format and materials and methods for using the format in a variety of applications. More particularly, the present invention provides single-layer lateral flow formats, materials and methods for detecting the presence of an analyte using a test strip comprising a dry porous medium comprising a single hydrophilic matrix. Devices are also provided as well as methods of making and using the format. The format is particularly useful for diagnosis of physiological and genetic conditions. In addition, the present invention provides methods and materials for concentrating a reagent in a porous medium.