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Activity Number: 637
Type: Topic Contributed
Date/Time: Thursday, August 7, 2014 : 10:30 AM to 12:20 PM
Sponsor: Section on Medical Devices and Diagnostics
Abstract #311394 View Presentation
Title: Coefficient of Variation (Cv) - What Does it Measure in a Quantitative Polymerase Chain Reaction (Qpcr) Assay?
Author(s): Jeng Mah*+
Companies: Beckman Coulter
Keywords: Coefficient of variation ; Precision and reproducibility ; Measurement scales ; Clinical applicability
Abstract:

In a real-time qPCR assay, the measurand, typically a trace amount of a certain DNA or RNA molecule, is replicated repeatedly for measurement. The original concentration of the target molecule X0 is quantified by the number of cycles Ct taken to reach a predetermined threshold Xt = X0 [1 +E]Ct, where E is a replication efficiency constant. This mechanism suggests a logarithmic link between the observable random variables, Ct, and the clinically meaningful concentration (X0). Conventionally, log10(X0), i.e. log10(X0) = log10(Xt) - Ct log10(1+E), and X0 are both used in reporting qPCR assay results. While X0 and log10(X0) are easily interchangeable, their statistics-especially the coefficient of variation, CV, which is an important measurement for precision and reproducibility of an assay-are not, either in magnitude or in meaning.

In this study, we characterize algebraic and interpretational differences between CVs computed from X0 and log10(X0) for evaluating the reproducibility of a qPCR assay. Effectiveness of different approaches given the presence of random measuring errors is discussed.


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