The Navigation Guide Systematic Review Methodology Proof of Concept: PFOA and Fetal Growth

Review All EHP content is accessible to individuals with disabilities. A fully accessible (Section 508–compliant) HTML version of this article is available at http://dx.doi.org/10.1289/ehp.1307893. The Navigation Guide—Evidence-Based Medicine Meets Environmental Health: Systematic Review of Human Evidence for PFOA Effects on Fetal Growth Paula I. Johnson, 1 Patrice Sutton, 1 Dylan S. Atchley, 1 Erica Koustas, 2 Juleen Lam, 2 Saunak Sen, 3 Karen A. Robinson, 4,5,6 Daniel A. Axelrad, 7 and Tracey J. Woodruff 1 1 Program on Reproductive Health and the Environment, University of California, San Francisco, Oakland, California, USA; 2 Oak Ridge Institute for Science and Education (ORISE) Postdoctoral Fellowship, National Center for Environmental Economics, Office of Policy, U.S. Environmental Protection Agency, Washington, DC, USA; 3 Department of Epidemiology and Biostatistics, University of California, San Francisco, San Francisco, California, USA; 4 Department of Medicine, 5 Department of Epidemiology, and 6 Department of Health Policy & Management, Johns Hopkins University, Baltimore, Maryland, USA; 7 National Center for Environmental Economics, Office of Policy, U.S. Environmental Protection Agency, Washington, DC, USA B ackground : The Navigation Guide methodology was developed to meet the need for a robust method of systematic and transparent research synthesis in environmental health science. We conducted a case study systematic review to support proof of concept of the method. O bjective : We applied the Navigation Guide systematic review methodology to determine whether developmental exposure to perfluorooctanoic acid (PFOA) affects fetal growth in humans. M ethods : We applied the first 3 steps of the Navigation Guide methodology to human epidemiological data: 1) specify the study question, 2) select the evidence, and 3) rate the quality and strength of the evidence. We developed a protocol, conducted a comprehensive search of the literature, and identified relevant studies using pre­specified criteria. We evaluated each study for risk of bias and conducted meta-analyses on a subset of studies. We rated quality and strength of the entire body of human evidence. R esults : We identified 18 human studies that met our inclusion criteria, and 9 of these were combined through meta-analysis. Through meta-analysis, we estimated that a 1‑ng/mL increase in serum or plasma PFOA was associated with a –18.9 g (95% CI: –29.8, –7.9) difference in birth weight. We concluded that the risk of bias across studies was low, and we assigned a “moderate” quality rating to the overall body of human evidence. C onclusion : On the basis of this first application of the Navigation Guide systematic review methodology, we concluded that there is “sufficient” human evidence that developmental exposure to PFOA reduces fetal growth. C itation : Johnson PI, Sutton P, Atchley DS, Koustas E, Lam J, Sen S, Robinson KA, Axelrad DA, Woodruff TJ. 2014. The Navigation Guide—evidence-based medicine meets environmental health: systematic review of human evidence for PFOA effects on fetal growth. Environ Health Perspect 122:1028–1039; http://dx.doi.org/10.1289/ehp.1307893 Introduction Synthesizing environmental health research from multiple streams of evidence is critical to translating the science into improved health outcomes. Robust, systematic, and transparent methods of research synthesis are an identi­ fied need in environmental health (National Research Council 2011). Such methods already exist to evaluate clinical evidence (GRADE Working Group 2012; Higgins and Green 2011) and include steps such as developing a pre­specified protocol, a compre­ hensive search, and rating the quality of the evidence. Although methods of synthesizing clinical research are primarily applied to randomized controlled clinical trials, the evidence streams for environ­mental health science are different. The Navigation Guide systematic review methodology was developed to apply best practices in research synthesis in clinical medicine and environ­mental health to the evidence streams common in environ­ mental health science (i.e., experimental toxi­ cological studies and observational human studies) in order to reach an overall conclusion about the strength of evidence (Woodruff et al. 2011a). Additional background on the Navigation Guide is given in a companion commentary (Woodruff and Sutton 2014). We undertook a case study to apply the Navigation Guide methodology. For this first case study, we evaluated the evidence for the effects of exposure to perfluoro­octanoic acid (PFOA) on fetal growth. PFOA has been used for > 50 years in the manufacture of fluoro­ polymers used in industrial applications and consumer products to impart certain charac­ teristics, such as fire and stain resistance [Prevedouros et al. 2006; U.S. Environmental Protection Agency (EPA) 2012]. We selected PFOA for evaluation based on pervasive human exposure and the evidence of asso­ ciations with fetal growth (Agency for Toxic Substances and Disease Registry 2009; Apelberg et al. 2007; Fei et al. 2007, 2008; Kato et al. 2011; U.S. EPA 2012). In addition, Address correspondence to P.I. Johnson, California Department of Public Health, Occupational Health Branch, 850 Marina Bay Parkway, Building P, Richmond, CA 94804 USA. Telephone: (510) 620-5711. E-mail: paula.johnson@cdph.ca.gov Supplemental Material is available online (http://dx.doi.org/10.1289/ehp.1307893). We acknowledge the following persons for their contributions: K. Guyton [National Center for Environmental Assessment, Washington Division, Office of Research and Development, U.S. Environmental Protection Agency (EPA)] for assistance with developing evidence evaluation methodologies and identifying relevant toxicological databases; K. Thayer, A. Rooney, and A. Boyles (Office of Health Assessment and Translation, National Toxicology Program), L. Bero [Department of Clinical Pharmacy, University of California, San Francisco (UCSF)], and L. Zeise (Reproductive and Cancer Hazard Assessment Branch, Office of Environmental Health Hazard Assessment, California Environmental Protection Agency) for assistance with developing risk of bias and evidence evaluation criteria; C. Lau (National Health and Environmental Effects Research Laboratory, Office of Research and Development, U.S. EPA) served as a perfluoro­octanoic acid (PFOA) subject matter expert; T. Horvath (Prevention and Public Health Group, and Co-Managing Editor of the Cochrane Review Group on HIV/AIDS at UCSF) for training and assistance with developing our search strategy; J. Pan (UCSF) for assistance with data extraction and thoughtful comments. Finally, we are grateful to M.-H. Chen, K. Choi, L.R. Goldman, R. Kishi, J.-H. Lee, and M. Marcus for their kind and timely response to requests for additional data and information and to the anonymous reviewers who helped to improve this manuscript. This research was funded through grants from New York Community Trust and the U.S. EPA through a contract with Abt Associates (GAIA-0-6-UCSF 17288). E.K. and J.L. were supported in part by appointments to the Internship/Research Participation Program at the National Center for Environmental Economics, U.S. EPA, administered by the Oak Ridge Institute for Science and Education through an interagency agreement between the U.S. Department of Energy and the U.S. EPA. For 2009–2013, support for the development and dissemination of the Navigation Guide methodology was provided by the Clarence Heller Foundation, the Passport Foundation, the Forsythia Foundation, the Johnson Family Foundation, the Heinz Endowments, the Fred Gellert Foundation, the Rose Foundation, Kaiser Permanente, the New York Community Trust, the UCSF Institute for Health Policy Studies, Planned Parenthood Federation of America, National Institute of Environmental Health Sciences (ES018135 and ESO22841), and U.S. EPA STAR grants (RD83467801 and RD83543301). T.J.W is a faculty member at the Philip R. Lee Institute for Health Policy Studies, UCSF. The contents of this paper are solely the responsibility of the authors and do not necessarily represent the official views of the U.S. EPA. Further, the U.S. EPA does not endorse the purchase of any commercial products or services mentioned in the publication. The authors declare they have no actual or potential competing financial interests. Received: 15 November 2013; Accepted: 23 June 2014; Advance Publication: 25 June 2014; Final Publication: 1 October 2014. volume 122 | number 10 | October 2014 • Environmental Health Perspectives