Abstract: A diagnostic device which enables measurement of fibrinogen concentration in a blood sample. The device comprises; a wettable testing substrate including viewing indicators which allow determination of a status of a test. The substrate has a first end and second end and intermediate therebetween a flow receiving zone, a flow path zone and a reaction zone; the reaction zone pre charged with at least one reagent. A blood sample to be tested is deposited near or in either of said flow receiving zone or said reaction zone, the sample reacting with the reagents inducing clotting of the sample. Water added to a dye added to said reaction zone, advances a distance along said substrate. The distance travelled along the substrate by the dye and through the sample is indicative of a measure of concentration of fibrinogen in said blood sample under test.