Normalized Tm Calling for Precise PCR Analyte Identification
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Solution Overview
Problem
Current PCR systems face challenges in distinguishing between closely related pathogens due to broad Tm value ranges, leading to difficulties in accurately identifying target nucleic acid sequences, especially when variations in pouch chemistry, amplicon amounts, and instrument characteristics affect melting temperatures.
Innovation Solution
Generate an array-specific range of Tm values by using a control sample to calculate a relationship between identified and expected Tm values, narrowing the range for improved specificity and sensitivity in identifying target nucleic acid sequences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a broad range of Tm values is used to identify target nucleic acid sequences, then the system maintains reliability across variations in pouch chemistry, amplicon amounts, and instrument characteristics, but the ability to distinguish between closely related pathogens deteriorates
Solution Approach 1:
The system performs preliminary normalization of Tm values using control samples before final pathogen identification. By pre-calculating normalization factors from control Tm values and applying them to all analyte Tm values, the system proactively compensates for run-to-run variations, enabling both broad reliability and precise discrimination between closely related pathogens.
Solution Approach 2:
Control samples serve as intermediaries between the variable experimental conditions and the target nucleic acid identification. The control Tm values mediate the normalization process, allowing the system to account for variations in pouch chemistry, amplicon amounts, and instrument characteristics without compromising the ability to distinguish between closely related pathogens.
2Measurement precision
If a narrow range of Tm values is used to improve specificity between related pathogens, then the ability to distinguish between closely related pathogens improves, but the system becomes more sensitive to variations in pouch chemistry, amplicon amounts, and instrument characteristics
Solution Approach 1:
The system uses control samples to provide feedback about actual run conditions and calculates normalization factors based on deviations from expected control Tm values. This feedback mechanism allows the system to dynamically adjust Tm ranges for analyte samples, maintaining narrow specific ranges while compensating for variations in pouch chemistry, amplicon amounts, and instrument characteristics through the calculated normalization factors.
3Reliability
If traditional broad Tm value ranges are used, then the system is robust against variations in experimental conditions, but false positives and false negatives increase
Solution Approach 1:
The system changes the Tm parameter from absolute values to normalized values by calculating the difference between analyte Tm and control Tm (or applying normalization factors). This parameter transformation maintains robustness against variations in experimental conditions while reducing false positives and false negatives, as the normalized Tm differences are less susceptible to run-to-run variations.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The method enhances the ability to distinguish between related pathogens by providing a narrower, array-specific Tm value range, improving diagnostic accuracy and reducing false positives/negatives.
Implementation Method 1
measuring, by an optical system, fluorescent data during or subsequent to the amplification of the control sample
Implementation Method 2
amplifying the control sample by thermal cycling the control sample well
Implementation Method 3
identifying, by the processor, based on the control melting curve, a Tm value for the control sample
Data Source
AI summary
Techniques are provided for generating an array-specific range of Tm values to be used for calling a sample in a given array positive or negative for a target nucleic acid sequence. A sample well in an array is provided with a control sample containing a control nucleic acid sequence. The control sample is amplified by thermal cycling the sample well. A Tm value for the control sample is identified and compared to an expected Tm value for the control nucleic acid sequence to calculate a relationship between the identified control Tm value and the expected control Tm value. By applying this relationship to an expected Tm value for a target nucleic acid sequence, an array-specific range of Tm values for the target nucleic acid sequence is generated and can be used for calling an experimental sample in the same array positive or negative for the target nucleic acid sequence.