A Tier 1 study would include samples with a known history and doc

A Tier 1 study would include samples with a known history and documented

stability data. Tier 2 studies have known Lapatinib price losses during storage but the difference between low and high exposures can be qualitatively assessed (i.e., for the purposes of the study, it is sufficient to bin study participants as having either low or high exposure). Tier 3 studies use samples with either unknown history and/or no stability data for the analyte(s) of interest. This BEES-C evaluative criterion is one of the most critical criteria for evaluating studies measuring ubiquitous short-lived chemicals. This is because the likelihood of sample contamination from the time of collection to the time of measurement has been demonstrated for many of these chemicals, this in spite of great lengths taken to avoid contamination. A wide range of chemicals with short physiologic half lives are not only environmentally ubiquitous but may also be present in the sampling and analytical equipment used in epidemiological research. Thus, extreme care is necessary in order to avoid/prevent sample contamination during all phases of a study from sample collection to sample buy Veliparib measurement (Barr et al., 1999,

Calafat and Needham, 2008, Calafat and Needham, 2009 and Needham et al., 2007). During sample collection, supplies containing the target chemical or exposing the collection materials or matrix to environmental media (e.g., air or water) can falsely elevate the measured concentrations. Even with precautions, studies have

reported difficulties with analytic contamination, contributing to uncertainty in interpretation of study results. Ye et al. (2013) note that despite their best efforts, samples at the Centers for Disease Control Prevention laboratory were contaminated with triclosan; the source of the contamination was ultimately identified as a triclosan-containing handsoap used by a technician. Similarly, several research groups have noted the difficulties in attempting to measure BPA in blood samples, in part, because of contamination (including in solvents and reagents) despite great care taken to avoid such contamination (Calafat et al., 2013, Markham et al., 2010, Teeguarden et al., Adenosine triphosphate 2011 and Ye et al., 2013). A Tier 1 study ensures the samples are contamination-free from time of collection to time of measurement (e.g., by use of certified analyte-free collection supplies and reference materials, and appropriate use of blanks both in the field and lab). The research will include documentation of the steps taken to provide the necessary assurance that the study data are reliable and accurate. Any study not using/documenting these procedures is categorized as Tier 2. In a Tier 3 study, there are known contamination issues and no documentation that the issues were addressed.

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