Patent ID: 7729866

Claim:
A method of determining the concentration of a particular component in a blood sample, comprising: (1) determining a calibration curve for a measuring device by (a) analyzing a blood sample that has a known concentration of the component using an electrode specifically sensitive to the component, (b) obtaining a time series of outputs from the electrode, (c) calculating an apparent component concentration at the time of equilibrium as measured by the electrode, (d) computing the concentration at which the first or second derivative of the time series reaches a maximum, (e) generating a set of calibration data by repeating steps (a)-(d) with samples of varying known component concentrations, (f) and fitting the resulting calibration data to the relational expression ((S−DI)/(S−EP))=a×S+b, wherein (i) S is the known concentration of the component in the sample, (ii) DI is the concentration at which the derivative reaches the maximum, (iii) EP is the apparent component concentration at the equilibrium point, (iv) a and b are parameters calculated by least-squares fitting; and (g) storing a and b as calibration parameters in the measuring device; and (2) using the calibrated measuring device to (a) analyze a blood sample that has an unknown concentration of the component using an electrode specifically sensitive to the component, (b) obtain a time series of outputs from the electrode, (c) calculate an apparent component concentration at the time of equilibrium as measured by the electrode, (d) compute the concentration at which the first or second derivative of the time series reaches a maximum, (e) solve the expression ((S−DI)/(S−EP))=a×S+b for S, wherein (i) DI is the concentration at which the derivative reaches the maximum, (ii) EP is the apparent component concentration at the equilibrium point, (iii) a and b are the stored calibration parameters, and (iv) S is the concentration of the component in the sample; and (f) calculate the true concentration of component in the blood sample.