Disposable urea sensor and system for determining creatinine and urea nitrogen-to-creatinine ratio in a single device

1. A disposable urea sensor comprising:

a laminated body having a fluid sample inlet end and an electrical contact end, said laminated body includes a base layer, a reagent holding layer with cutouts defining a working electrode and a reference electrode, a channel forming layer and a cover;

a fluid sample inlet at said fluid sample inlet end;

a substantially flat sample chamber in communication between said fluid sample inlet and a vent opening wherein said sample chamber is adapted to collect a fluid sample through said fluid sample inlet, said substantially flat sample chamber defined by said base layer, said reagent holding layer, said channel forming layer and said cover;

a working electrode and a reference electrode within said sample chamber; and

a dissolvable mixture of a reagent matrix disposed directly on said working electrode wherein said reagent matrix contains urease but absent any redox mediator and a dissolvable mixture of a reference matrix disposed directly on said reference electrode wherein said reference matrix contains a redox mediator.

2. The sensor of claim 1 wherein said reagent matrix further includes one or more of the materials selected from the group consisting of a binder, a buffer, a surfactant, a stabilizer, and a bulking agent.

3. The sensor of claim 2 wherein said binder is a cellulose material.

4. The sensor of claim 3 wherein said cellulose material is hydroxypropyl cellulose.

5. The sensor of claim 1 further comprising a blank electrode and a second reagent matrix disposed on said blank electrode wherein said second reagent matrix includes a buffer.