When using evidence from non-randomized studies (NRS) to answer questions about the effects of environmental exposures on health, it is important to assess risk of bias (RoB) of individual studies as part of determining the certainty in the body of evidence. The recently released RoB in Non-randomized Studies of Interventions (ROBINS-I) instrument has undergone careful development and piloting on NRS of health interventions. A key feature of ROBINS-I is evaluating the RoB of studies against an ideal target trial, therefore establishing a structured comparison of RoB against a reference standard. While several instruments exist to evaluate the RoB of NRS of exposure, none of them use such a structured comparison of RoB. Using the fundamental design of ROBINS-I, we explored development of a version of the instrument to evaluate RoB in studies of environmental exposure. We identified important modifications necessitating a distinct instrument: The RoB instrument for NRS of exposures.
This work highlights the importance of standardized methods for environmental health decision making, proposes a modified instrument to evaluate the RoB of NRS of exposures, provides guidance for the implementation of the instrument and integration into structured evidence-synthesis frameworks (such as GRADE [Grading of Recommendations Assessment, Development and Evaluation]), and presents evidence on the reliability and validity of the instrument. The RoB instrument for NRS of exposures delivers a standardized instrument that systematic review authors and guideline developers can use to evaluate RoB in NRS of exposures. The nature of these methodological changes allow better integration of RoB assessment in the environmental health field with GRADE. / Thesis / Doctor of Philosophy (PhD) / When making a decision about interventions to reduce or remove an environmental exposure, evidence is needed to weigh the desirable and undesirable consequences of the decision. No research study is perfect. Most of the studies documenting environmental exposures cannot control for the fact that people who might be highly exposed may have different characteristics compared to those who have low levels of exposure other than just the exposure itself. For example, people exposed to more environmental air pollution living in inner cities may also be more likely to smoke or have occupational exposures that could predispose them to lung cancer than those exposed to lower levels of air pollution. Understanding limitations in studies that address those questions informs our certainty that the data represents the truth. The greater the confidence we have in the data, the more likely we are to be certain that removing or reducing exposure will lead to a desirable outcome. A tool can be used to walk people through the evaluation of limitations within each study. However, it is important that the tool evaluates the correct limitations within the study. It is also important that people using the tool can apply it reliably. Without a reliable or valid tool to evaluate the limitations of the studies, it can be difficult to inform decisions on whether or not to implement specific policies.
In our study, we tested the ability of a new and well-developed tool (ROBINS for interventions) to identify the limitations in studies linking environmental exposures to health outcomes. Based on the findings from our evaluation, we modified our protocol to see if we could improve our ability to evaluate these studies of environmental exposures. We asked people with an understanding of scientific methods to independently evaluate 35 studies with our modified tool (ROBINS for exposures). We compared those responses to see whether all the reviewers came up with similar decisions and if their decision was similar or different than the conclusion they made using more commonly used tools.
Based on our results, we determined that our modified tool does provide a consistent evaluation of study limitations and accurately measures the limitations present in studies of exposure. This tool can be used to inform decisions about removing or reducing one’s exposure to environmental hazards.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/22877 |
| Date | January 2018 |
| Creators | Morgan, Rebecca L. |
| Contributors | Schünemann, Holger J., Health Research Methodology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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