Abstract: The present invention relates to an assay device comprising a multilayer support upon which a first analyte-binding compound (or complex) is immobilized in one or more test zone(s), wherein said first analyte-binding compound is capable of binding an analyte present in a test sample, wherein said analyte binds a second analyte-binding compound (or complex) to form a sandwich complex on said zone, with said second analyte-binding compound being labeled by an enzyme; and wherein said sandwich complex produces upon contact with a precipitating substrate for said enzyme-label a colored deposit. The invention also relates to a diagnostic kit or a method for the detection of an analyte in any medium.