Using evidence mapping to focus and refine the evaluation of reproductive endpoints in a systematic review of PCBs poster
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Systematic review will often reveal a wide range of health outcomes associated with exposure to a
chemical of interest. This is particularly true for chemicals that have thousands of studies available,
such as polychlorinated biphenyls (PCBs). From a pragmatic perspective, a systematic review of all of
these studies is not feasible. In such cases, it may be helpful to focus the systematic review on the
outcomes identified as most impactful for protecting public health. Here, we describe the application of
evidence mapping as an organizational principle for refining a large and complex database, using animal
toxicology studies on the reproductive effects of PCBs as an example. A systematic review of PCB-related
health effects identified >400 animal toxicology studies that evaluated reproductive toxicity.
These studies were extracted into a literature inventory designed to capture relevant experimental
design and health outcome details. The endpoints evaluated in each study were categorized according to
type of outcome (e.g. fertility/fecundity, hormone levels, organ weights). To identify the most relevant
adverse health outcomes to move forward for further evaluation, major considerations will include the
number and types of studies evaluating each outcome, the severity or biological significance of each
outcome, and the relative sensitivity of each outcome to PCB exposure. Once the most relevant adverse
health outcomes are identified, studies reporting these outcomes can proceed through the systematic
review process, where they will undergo study evaluation and further analysis