PCR elbow determination by use of a double sigmoid function curve fit with the Levenburg-Marquardt algorithm and normalization

A tangible computer-readable medium that stores code for controlling a processor to determine a point at the end of the baseline region of a growth curve, the code including instructions to:

• receive a dataset representing a growth curve, said dataset including a plurality of data points each having a pair of coordinate values;
• calculate an approximation of a curve that fits the dataset by applying a Levenberg-Marquardt (LM) regression process to a double sigmoid function to determine parameters of the function;
• normalize the curve using the determined parameters to produce a normalized curve;
• process the normalized curve to determine a coordinate value of a point at the end of the baseline region of the growth curve;
• and
• output the coordinate value to a display device.

A kinetic Polymerase Chain Reaction (PCR) system, comprising:

• a kinetic PCR data acquisition device that generates a PCR dataset representing a kinetic PCR amplification curve, said dataset including a plurality of data points, each having a pair of coordinate values, wherein said dataset includes data points in a region of interest which includes a cycle threshold (Ct) value;
• and
• a processor adapted to receive and to process the PCR dataset to determine the Ct value, by:
• calculating an approximation of a curve that fits the dataset by applying a Levenberg-Marquardt (LM) regression process to a double sigmoid function to determine parameters of the function;
• normalizing the curve using the determined parameters to produce a normalized curve;
• and
• processing the normalized curve to determine a coordinate value of a point at the end of the baseline region of the growth curve, Wherein said point represents the cycle threshold (Ct) value of the growth curve.