may have been exposed to sarin as a result of terrorist activity, healthy volunteers (including military populations), and clinical populations (e.g., patients with myasthenia gravis treated with PB). Studying these groups allowed the committee to address the issue of whether the agents could be associated with adverse health outcomes.

In this chapter, the committee describes its approach to enable the reader to assess and interpret its findings and to assist those who may update the committee’s conclusions as new information becomes available. The details of the analysis related to each agent and conclusions concerning health effects appear in subsequent chapters and in the Executive Summary. The committee’s analyses have both quantitative and qualitative aspects, and reflect the evidence and the approach taken to evaluate that evidence. The methodology described in this chapter, draws from the work of previous Institute of Medicine (IOM) committees and their reports on vaccine safety (IOM, 1991, 1994a), herbicides used in Vietnam (IOM, 1994b, 1996, 1999), and indoor pollutants related to asthma (IOM, 2000). However, the conclusions in the current report depart from previous studies by distinguishing between transient and long-term health effects, and dose-related health outcomes as they are reported in the literature.

METHODS OF GATHERING AND EVALUATING THE EVIDENCE

The committee reviewed and evaluated studies from the scientific and medical literature that were identified by searches of bibliographic databases and other methods (see Appendix C). As noted, the committee did not limit its review to health effects reported by Gulf War veterans but studied all health outcomes reported in populations exposed to the agents of concern. By taking this broad and inclusive approach the committee intends to provide the Department of Veterans Affairs (VA) with a range of information about potential health outcomes for their consideration as they develop a compensation program for Gulf War veterans. Further, studies of nonveteran populations are also important for understanding those health effects with a long latency period between the time of exposure to the agent and the health effect (e.g., cancer) since long-term effects might not yet be manifest in Gulf War veterans, yet could be important for compensation decisions later in life.

The committee adopted a policy of using only peer-reviewed published literature as the basis for its conclusions. Publications that were not peer-reviewed had no evidentiary value for the committee (i.e., they were not used as evidence for arriving at the committee’s conclusions about the degree of association between exposure to a particular agent and adverse health effects). The process of peer review by fellow professionals, which is one of the hallmarks of modern science, ensures high standards of quality but does not guarantee the validity or generalizability of a study. Accordingly, committee members read each article critically. In some instances, non-peer-reviewed publications provided background information for the committee and raised issues that required further



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