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Activity Number: 25
Type: Topic Contributed
Date/Time: Sunday, August 4, 2013 : 2:00 PM to 3:50 PM
Sponsor: Section on Statistics in Epidemiology
Abstract - #308241
Title: The Effect of Precision at the Decision Point on Diagnostics Accuracy of a Biomarker Assay
Author(s): Jeng Mah*+
Companies: Beckman Coulter, Inc.
Keywords: Relative Precision ; Cutoff Point ; Sensitivity/Specificity ; Cost/Benefit ; Optimal Decision

The diagnostic accuracy of an assay is a function of the cutoff point (CoP) and precision of the measurements. An assay aims to detect a disease marker that is absent or barely traceable in healthy subjects, e.g. Human Immunodeficiency Virus (HIV) or prostate specific antigen (PSA), the CoP for a negative diagnosis is limited by the assay's detection limit. Assay precision is especially critical around the CoP because any measurement error at such low levels may translate to a false positive result. Precision and CoP are both primary interests of a bio-marker assay; however, the precision, CoP, and accuracy of an assay are typically evaluated separately, and thus the effects of precision and CoP on diagnostic accuracy are poorly known.

We examine theoretical and empirical effects of relative precision (correlation of variation, CV) and CoP on the diagnostic accuracy of an assay using simulated data. Special focus is put on defining cost/benefit, measured both in sensitivity/specificity and the expected losses of incorrect decisions, as a function of CoP and CV. The formulation of an optimal decision rule with respect to expected loss, considering CoP and CV, is also discussed.

Authors who are presenting talks have a * after their name.

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