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Stat Med. 2013 Dec 10;32(28):4995-5007. doi: 10.1002/sim.5872. Epub 2013 Jun 20.

Change-point models to estimate the limit of detection.

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The EMMES Corporation, Rockville, Maryland 20850, U.S.A.


In many biological and environmental studies, measured data is subject to a limit of detection. The limit of detection is generally defined as the lowest concentration of analyte that can be differentiated from a blank sample with some certainty. Data falling below the limit of detection is left censored, falling below a level that is easily quantified by a measuring device. A great deal of interest lies in estimating the limit of detection for a particular measurement device. In this paper, we propose a change-point model to estimate the limit of detection by using data from an experiment with known analyte concentrations. Estimation of the limit of detection proceeds by a two-stage maximum likelihood method. Extensions are considered that allow for censored measurements and data from multiple experiments. A simulation study is conducted demonstrating that in some settings the change-point model provides less biased estimates of the limit of detection than conventional methods. The proposed method is then applied to data from an HIV pilot study.


change point; limit of detection; linear calibration curve; two-stage maximum likelihood

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