Patent ID: 7739054

Claim:
A method for determining the amount of a nucleic acid in a test sample, comprising the steps of: amplifying a predetermined locus of the nucleic acid in an in vitro amplification reaction to create a nucleic acid amplification product; determining a value proportional to the amount of the nucleic acid amplification product present at different times during the in vitro amplification reaction, whereby there is created a collection of time-dependent values that collectively define a growth curve; performing a vector analysis on at least a portion of said growth curve to identify a time-dependent feature indicating a transition from the baseline phase into the growth phase of said growth curve, said vector analysis comprising the steps of, (a) establishing a plurality of pairs of first and second vectors at different points on a time dimension of the growth curve using said collection of time-dependent values, wherein each vector of a single pair of vectors among said plurality has the same origin, and wherein the head of the first vector and the head of the second vector of said single pair of vectors among said plurality are each positioned at different points on the growth curve, (b) calculating for each pair of vectors the value of an angle therebetween, thereby resulting in a plurality of calculated angles, with each point on the time dimension of the growth curve being associated with a different one of said plurality of calculated angles, (c) comparing the plurality of calculated angles with each other to identify a characteristic angle, and (d) identifying said time-dependent feature of said growth curve as the point on the time dimension of the growth curve that is associated with the characteristic angle, said characteristic angle being either the maximum angle among the plurality of calculated angles or the minimum angle among the plurality of calculated angles; comparing the time-dependent feature identified in step (d) with a standard calibration curve; and determining from said time-dependent feature of said growth curve and said standard calibration curve the amount of the nucleic acid in the test sample.