Method for correcting Crea sensor for calcium inhibition

A method of calibrating a device for measuring concentration of creatine and/or creatinine in a sample including one or more enzyme modulators, the method comprising:

• providing a device for measuring concentration of creatine and/or creatinine in a sample, wherein the device comprises an enzyme layer;
• aspirating an earlier sample in the device and estimating a first concentration of an enzyme modulator remaining in the enzyme layer;
• providing one or more calibration solutions;
• determining a sensitivity of the device for each of the one or more calibration solutions;
• determining a degree of modulation for the sample to be measured;
• determining a degree of modulation for each of the one or more calibration solutions;
• wherein said determining a degree of modulation for each of the one or more calibration solutions comprises estimating a second concentration of the enzyme modulator in the enzyme layer of the device corrected by said first concentration;
• wherein the one or more enzyme modulators comprise Ca2+, Mg2+, and salts thereof;
• and
• calculating the sensitivity of the device for the sample, wherein said calculating comprises adjusting the sensitivity of the device for each of the one or more calibration solutions by a factor comprising the determined degree of modulation of the sample and the one or more calibration solutions.