Method and device for measuring the fibrinogen concentration in blood samples

A disposable diagnostic indicator device which enables measurement of fibrinogen concentration in a blood plasma sample applied to said device, the indicator comprising:

• a wettable porous testing substrate, the porous testing substrate having a first end and second end and intermediate therebetween a flow receiving zone, a flow path zone and a reaction zone;
• the reaction zone of the substrate pre charged with Thrombin and an indicating dye;
• wherein, when said sample is deposited in said flow receiving zone or in said reaction zone, a zone of hydrophobicity is created;
• and wherein when water mixes with the dye, the dye advances along the flow path zone;
• also urging said sample a distance along said substrate, the distance travelled along said substrate of the indicating dye providing a measure of concentration of fibrinogen in said blood sample under test.

A method of testing for the concentration of fibrinogen in a blood sample using a diagnostic device which enables measurement of fibrinogen concentration in the blood sample, the device comprising;

• a wettable testing substrate and a housing including viewing indicators which allow determination of a status of a test;
• the substrate having 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 reagents;
• the method comprising the steps of:
• a) pre charging said porous substrate with Thrombin chromogenic substrate and a dye/buffer solution, to provide a reagent reaction mixture in a reaction zone;
• b) adding a blood or plasma sample near or in said receiving zone or near or in said reaction zone so that is engages with the reagent;
• c) allowing the plasma to react with the thrombin to create a zone of hydrophobicity and induce clotting;
• d) using the porosity in the substrate to transport the dye/buffer solution along the substrate and through the reaction zone,
• e) observing a distance along the porous substrate that the dye/buffer solution passes;
• f) determining fibrinogen concentration in said sample with reference to said distance that the dye/buffer solution travels along the flow path zone.

A testing method for determining the concentration of fibrinogen in a test sample using a porous substrate;

• the substrate having a first end and second end and intermediate therebetween a flow receiving zone, a flow path zone and a reaction zone;
• the method comprising the steps of:
• g) pre charging said porous substrate with Thrombin chromogenic substrate to provide a reaction zone and an indicating dye;
• h) adding a plasma sample to said reaction zone;
• i) allowing the plasma to react with the thrombin to clot and create a zone of hydrophobicity;
• j) washing the dye/buffer solution in the reaction zone,
• k) observing a distance that the dye/buffer solution travels along the flow path zone and any colour change;
• l) determining fibrinogen concentration in said sample with reference to said distance and/or said colour change.

The method according to claim 39 wherein said diagnosis of fibrinogen concentration can be made using the following combined three mechanisms;

• 1) a change in dye adhesiveness induced by polymerization of the fibrinogen in the blood sample to fibrin upon enzymatic reaction with thrombin and/or FXIIIa deposited onto the receiving zone;
• 2) adhesion of the dye deposited in the receiving zone to the fibrin directly (or indirectly via the assistance of dye binders);
• and
• 3) capillarity used to distribute the blood sample into the receiving zone treated with thrombin, and transport wash solution through the receiving surface to remove dye out of the porous material.