Abstract: A reaction surface array diagnostic apparatus and method of making the same includes a substrate carrying a plurality of reaction surfaces and a gasket having a plurality of through bores, each alignable with one of the reaction surfaces and forming a fluid tight well about each reaction surface when the gasket is sealingly affixed to the substrate. In one aspect, the gasket and the substrate are mounted in a support. In another aspect, a plate having a plurality of through bores is mountable on the gasket and substrate. Clamp members engage opposite side edges of the plate, the gasket and the substrate.