Patent ID: 8211363

Claim:
A sensor for determining the concentration of an analyte in a sample fluid, the sensor comprising: a proximal end and a distal end, the distal end being configured and arranged for insertion into a sensor reader, and the proximal end comprising first and second extensions on a first and second side edge of the sensor; an electrode pair comprising a working electrode and a counter electrode, wherein the working electrode and counter electrode are separated by an effective distance in a range of 25 to 1000 μm; a sample chamber for holding the sample fluid, the sample chamber comprising the working electrode and the counter electrode, wherein the sample chamber is sized to contain a volume of no more than about 1 μL of the sample; a first indicator electrode to indicate when the sample chamber is beginning to fill with sample; a second indicator electrode to indicate when the sample chamber is substantially filled with sample, wherein either the working electrode or the counter electrode is disposed between the first and second indicator electrodes; and an analyte-responsive enzyme and a diffusible redox mediator disposed in the sample chamber, the sensor having been configured and arranged so that a background signal generated by the diffusible redox mediator in the absence of the analyte is no more than 25% of the signal generated by oxidation or reduction of the average normal physiological amount of analyte.