Preanalytical considerations in the design of clinical trials and epidemiological studies.

Clinical trials and epidemiologic and most types of clinical research include the acquisition of biological samples to be analyzed either immediately after collection or in the future for biomarkers related to the study hypotheses. Tested biomarkers include those used to monitor subjects’ health and to detect harmful side effects (e.g., liver and kidney function tests) or to follow the impact of therapeutic interventions. These samples may also be used for biomarker discovery. Whatever the study goals may be, the quality of study outcomes will depend heavily on the quality of the samples obtained and subsequent analysis. Since the largest component of total error in the clinical laboratory has been found to be associated with the preanalytical phase, it is probably safe to assume that the same conclusion applies to clinical trials and epidemiologic studies. Although standardization of preanalytical variables is not a trivial manner, it is essential to ensure successful outcomes of these studies. The competency of personnel performing such testing, and their training and understanding of sample collection and processing procedures, must be assured. Samples must be handled in an identical fashion at all times and in all locations, and procedures must be in place to avoid sample mix-ups. These are only few of the challenges encountered during the preanalytical phase. In this Q&A, 5 experts with a vast experience in national and international biomarker studies provide their insights into the issue of preanalytical variables and how these can impact the design of clinical and epidemiologic studies.