Disclosed is a diagnostic testing device that may be used to detect one or more analytes in a sample. The device comprises a receptacle and a holder for a test strip. The test strip may be, for example, a lateral flow test strip. The device and holder permit analysis of a sample, wherein the device is substantially sealed during testing and detection of results. To use, the holder containing a test strip is inserted into the receptacle containing sample to be analyzed. Capillary flow along the test strip is initiated by contact of the sample with the distal end of the test strip. The receptacle is such that results of the assay may be detected visually or using standard instrumentation such as by measuring light absorption or reflectance.