The present invention relates to diagnostic methods utilizing an apparatus comprising a substrate having at least one assay station. The at least one assay station has at least a first assay station channel and at least a second assay station channel and the first and second assay station channels each separately being in communication with the at least one assay station. The apparatus has an arrangement of at least first and second multi-purpose channels in communication with the first and second assay station channels, respectively. The first multi-purpose channel and first assay station channel have internal surface characteristics conducive to conduction of a sample solution therethrough. There is at least one sample fluid inlet in communication with the at least first multi-purpose channel, and at least one isolation-medium inlet in communication with the at least first and second multi-purpose channels. The at least one second multi-purpose channel has an internal surface portion non-conducive to conduction of said sample solution.
