Evaluation of uncertainty in quantitative real-time PCR
John L Love1, Paula Scholes, Brent Gilpin
1Christchurch Science Centre, Institute of Environmental Science and Research Ltd., PO Box 29 181, Christchurch, New Zealand. jlove_nz@yahoo.com
Journal of Microbiological Methods
|June 1, 2006
Summary
Quantitative real-time PCR (qPCR) enables nucleic acid measurement, but requires uncertainty estimation. This study details the uncertainty budget for qPCR, revealing significant variability in DNA quantification, particularly for Campylobacter jejuni enumeration.
Area of Science:
- Molecular Biology
- Analytical Chemistry
- Microbiology
Background:
- Quantitative real-time PCR (qPCR) is a key technique for nucleic acid quantification in biological samples.
- Accurate interpretation of qPCR results necessitates a thorough understanding and estimation of measurement uncertainty.
- Previous studies have highlighted the need for robust uncertainty budgets in molecular diagnostic assays.
Purpose of the Study:
- To develop and present an uncertainty budget for quantitative real-time PCR (qPCR).
- To identify and quantify the main sources of uncertainty in qPCR-based DNA measurements.
- To exemplify the uncertainty budget using qPCR data for Campylobacter jejuni enumeration.
Main Methods:
- Development of an uncertainty budget based on the GUM (Guide to the Expression of Uncertainty in Measurement) principles.
- Application of the budget to experimental data from a qPCR assay targeting Campylobacter jejuni.
- Analysis of key parameters contributing to overall measurement uncertainty, including threshold cycle (Ct) values, calibration curves, and molar absorbance.
Main Results:
- The study identified significant uncertainty in qPCR measurements, with a notable example showing a 95% confidence interval of +/-84 units for a measured DNA result of 151 units.
- The primary contributors to uncertainty were determined to be the measurement of the threshold cycle (Ct) value, the prediction of DNA content from the calibration line, and the molar absorbance value of DNA.
- The developed uncertainty budget provides a framework for assessing the reliability of qPCR quantification.
Conclusions:
- Quantitative real-time PCR (qPCR) measurements inherently possess substantial uncertainty.
- Accurate DNA quantification using qPCR requires careful consideration and management of identified uncertainty sources.
- The findings are crucial for reliable microbial enumeration and molecular diagnostics, emphasizing the need for reporting uncertainty alongside results.
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