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Environ Int. 2016 Jul-Aug;92-93:617-29. doi: 10.1016/j.envint.2016.01.005. Epub 2016 Feb 6.

How credible are the study results? Evaluating and applying internal validity tools to literature-based assessments of environmental health hazards.

Author information

1
Office of Health Assessment and Translation, Division of the National Toxicology Program, National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Research Triangle Park, NC, USA.
2
National Center for Environmental Assessment, Office of Research and Development, U.S. Environmental Protection Agency, Washington, DC, USA.
3
Office of the Report on Carcinogens, Division of the National Toxicology Program, National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Research Triangle Park, NC, USA.
4
University of California San Francisco, Program on Reproductive Health and the Environment, San Francisco, CA, USA.
5
McMaster University, Department of Clinical Epidemiology and Biostatistics, Hamilton, Ontario, Canada.
6
Integrated Laboratory Systems (ILS), Morrisville, NC, USA.
7
Office of the Report on Carcinogens, Division of the National Toxicology Program, National Institute of Environmental Health Sciences (NIEHS), National Institutes of Health (NIH), Research Triangle Park, NC, USA. Electronic address: lunn@niehs.nih.gov.

Abstract

Environmental health hazard assessments are routinely relied upon for public health decision-making. The evidence base used in these assessments is typically developed from a collection of diverse sources of information of varying quality. It is critical that literature-based evaluations consider the credibility of individual studies used to reach conclusions through consistent, transparent and accepted methods. Systematic review procedures address study credibility by assessing internal validity or "risk of bias" - the assessment of whether the design and conduct of a study compromised the credibility of the link between exposure/intervention and outcome. This paper describes the commonalities and differences in risk-of-bias methods developed or used by five groups that conduct or provide methodological input for performing environmental health hazard assessments: the Grading of Recommendations Assessment, Development, and Evaluation (GRADE) Working Group, the Navigation Guide, the National Toxicology Program's (NTP) Office of Health Assessment and Translation (OHAT) and Office of the Report on Carcinogens (ORoC), and the Integrated Risk Information System of the U.S. Environmental Protection Agency (EPA-IRIS). Each of these groups have been developing and applying rigorous assessment methods for integrating across a heterogeneous collection of human and animal studies to inform conclusions on potential environmental health hazards. There is substantial consistency across the groups in the consideration of risk-of-bias issues or "domains" for assessing observational human studies. There is a similar overlap in terms of domains addressed for animal studies; however, the groups differ in the relative emphasis placed on different aspects of risk of bias. Future directions for the continued harmonization and improvement of these methods are also discussed.

KEYWORDS:

Environmental health; Hazard assessment; Internal validity; Risk of bias; Systematic review

PMID:
26857180
PMCID:
PMC4902751
DOI:
10.1016/j.envint.2016.01.005
[Indexed for MEDLINE]
Free PMC Article

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