Assays and methods including mobile tagged single stranded nucleic acid reagents pre-loaded on an analysis device, which are preferably tagged, but not labeled and are complementary to a strand (preferably the anti-sense strand in double stranded DNA targets) of the target nucleic acid. The assay also includes a running buffer that includes a dye or other detectable label that nonspecifically binds only to double stranded nucleic acids. In addition, the analysis device includes a detection zone including one or more test zones that have an immobilized tag that binds to the tag on the mobile nucleic acid reagent.