PCR elbow determination by rotational transform after zero slope alignment

A computer-implemented method of determining the cycle threshold (Ct) values for a plurality of the Polymerase Chain Reaction (PCR) curves, the method comprising:

• receiving a plurality of datasets, each data set representing a PCR curve, each said data set including a plurality of data points each having a pair of coordinate values, wherein each said dataset includes data points in a region of interest which includes the Ct value;
• and
• for each dataset:
• calculating an approximation of the curve by applying a Levenberg-Marquardt (LM) regression process to the data set and a double sigmoid function to determine parameters of the function;
• modifying the curve using the determined parameters to produce a modified dataset;
• applying a first rotational transformation to at least a portion of the modified data set including the region of interest to produce a transformed data set;
• identifying a data point in the transformed data set having at least one of a minimum coordinate value or a maximum coordinate value;
• applying a second rotational transformation, inverse to the first transformation, to the identified data point;
• and thereafter
• re-determining at least one coordinate value of the identified data point, wherein the re-determined coordinate value of the identified data point represents the Ct value for the PCR curve.

A computer-readable medium including code for controlling a processor to determine a cycle threshold (Ct) value in a kinetic Polymerase Chain Reaction (PCR) amplification curve, the code including instructions to:

• receive a data set representing a kinetic PCR amplification curve, said data set 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 the Ct value;
• calculate an approximation of the curve by applying a Levenberg-Marquardt (LM) regression process to the data set and a double sigmoid function to determine parameters of the function;
• modify the curve using the determined parameters to produce a modified dataset;
• apply a first rotational transformation to at least a portion of the modified data set including the region of interest to produce a transformed data set;
• identify a data point in the transformed data set having at least one of a minimum coordinate value or a maximum coordinate value;
• apply a second rotational transformation, inverse to the first transformation, to the identified data point;
• and thereafter
• re-determine at least one coordinate value of the identified data point, wherein the re-determined coordinate value of the identified data point represents the Ct value for the PCR curve.

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

• a kinetic PCR analysis module that generates a PCR data set 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 the region of interest which includes a cycle threshold (Ct) value;
• and
• an intelligence module adapted to process the PCR data set to determine the Ct value by:
• calculating an approximation of the curve by applying a Levenberg-Marquardt (LM) regression process to the data set and a double sigmoid fimction to determine parameters of the function;
• modifying the curve using the determined parameters to produce a modified dataset;
• applying a first rotational transformation to at least a portion of the modified data set including the region of interest tb produce a transformed data set;
• identifying a data point in the transformed data set having at least one of a minimum coordinate value or a maximum coordinate value;
• applying a second rotational transformation, inverse to the first transformation, to the identified data point;
• and thereafter
• re-determining at least one coordinate value of the identified data point, wherein the re-determined coordinate value of the identified data point represents the Ct value for the PCR curve.