Gulf area, treatments, studies of short-term health outcomes only, rehabilitation, social outcomes (for example, employment), impacts on families, or studies of long-term outcomes from known physical events, such as gun-shot wounds. After the removal of these studies, approximately 400 potentially relevant epidemiologic studies were obtained for review and evaluation. The titles and abstracts of studies that had not been obtained as full text were available to the committee for review. The 400 studies that were obtained as full text were objectively evaluated by the committee members without preconceived ideas about what health outcomes might be seen and what, if any, associations might be found between being deployed to the Gulf War and any health outcomes.

The committee adopted a policy of using only published or unpublished literature that had undergone rigorous peer review as the basis of its conclusions. An exception to this policy was the inclusion of a few government reports. While the process of peer review by fellow professionals increases the likelihood that high-quality studies will appear in the literature, it does not guarantee the validity of any particular study or the ability to generalize its findings. Accordingly, committee members read each study critically and considered its relevance and quality. The committee did not collect original data, nor did they perform any secondary data analyses.

After securing the full text of the relevant studies, the committee determined which health conditions it would focus upon in the report. Initially, the health conditions listed in Volume 4 were used but after reviewing numerous studies, new health outcomes were added, such as diseases of the blood and blood-forming organs and endocrine disorders. For each health outcome, one or more committee member with expertise or knowledge of a particular health outcome volunteered to screen all 400 studies in the database to identify all the epidemiologic studies that appeared to include information on that health outcome. The responsible committee member then conducted a preliminary review of the studies, including those cited in Volume 4, to determine what, if any, information the study had on the health outcome of interest and if an individual study met the inclusion criteria for a primary or secondary study (see below). The responsible committee member(s) then presented the information from the initial study screening and categorization to the full committee for discussion. Typically, the information presented included the populations used in the study, the methods for selecting and evaluating the populations, the study results, and the committee member’s assessment of the strengths and limitations of the study. Each primary and secondary paper was discussed for each health outcome. Because of the variability in the description and diagnosis of the health conditions considered in this report, it was impossible for the committee to make a priori assumptions about the utility of any paper for a health outcome; each paper was discussed individually for each health outcome. After the studies had been discussed in plenary session, the responsible committee member drafted the text for that health outcome; the draft text was reviewed and discussed in further plenary sessions until all committee members reach a consensus on the description of the studies and the summary and conclusions. After this language was agreed upon, the full committee assigned a category of association based on the number and quality of the primary and secondary studies and expert judgment. It should be noted that the committee did not use a formulaic approach as to the number of primary and secondary studies that would be necessary to assign a specific category of association. Rather the committee found that each health outcome required a more considered and nuanced approach as described in the summary and conclusion section.

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