Patent ID: 7788039

Claim:
A method for determining an amount of a target nucleic acid in a sample, comprising: generating signal data by performing a plurality of cycles of amplification on a target nucleic acid and a standard nucleic acid, the signal data including a series of standard signal values indicative of a quantity of the standard nucleic acid present during cycles of the standard amplification, and a series of target signal values indicative of a quantity of the target nucleic acid present during cycles of the target amplification; defining a target growth curve value using the target signal values and a standard growth curve value using the standard signal values, said defining comprising determining an elbow value for the standard nucleic acid or the target nucleic acid, wherein determining an elbow value includes interpolating between a number of a cycle for which the standard or target signal, respectively, is less than the predefined signal value and a number of a cycle for which the standard or target signal, respectively, is greater than the predefined signal value; and outputting a quantity indicative of an initial amount of the target nucleic acid according to a calculation that comprises use of a calibration equation, where the calibration equation is a nonlinear equation, wherein the calibration equation expresses quantity of target nucleic acid as a function of quantity of standard nucleic acid and difference in cycle numbers for standard and target nucleic acid, wherein the calculation comprises use of an initial amount of the standard nucleic acid for the quantity of the standard nucleic acid in the calibration equation and use of difference in the growth curve elbow values for the standard and target nucleic acid for the difference in the cycle numbers for the standard and target nucleic acid in the calibration equation to determine the initial amount of the target nucleic acid.