VA generally relies on major reports written by the Institute of Medicine (IOM, part of the National Academy of Sciences (NAS)) to determine which conditions are presumptive. IOM's contracts are written by OPH, and have been highly problematic and slanted against veterans since the beginning by the way they exclude what kinds of information an IOM panel can consider.
For example, when considering low-level chemical warfare agents like sarin, a known and VA-accepted 1991 Gulf War exposure, the IOM contract specifically and intentionally failed to allow the consideration of *animal* studies -- which make up the vast body of modern day medical research on the effects of chemical warfare agents. So, the IOM panel was unable to conclude any health effects associated with low-dose exposure to sarin, etc., and no new presumptives were made.
When VA fails to do proper epidemiological research (essentially mass surveys that identify what conditions or symptoms are more or less prevalent in the surveyed population), IOM panels have no research on which to base their determinations for new studies. When VA-OPH covers up or fails to publish findings from its epidemiologic studies, as was shown during the March 2013 Congressional hearing at which VA researcher-turned-whistleblower Dr. Steven Coughlin testified, then IOM panels again have no research studies to consider when they make their determinations.
And when VA-OPH fails to ask the right questions about symptoms, as they failed to do in their most recent follow-up (every 5 years) survey of 1991 Gulf War veterans, then information on the prevalence of GWI issues and diagnosed conditions is never found, and IOM panels again have no published research to review that would support new presumptive determinations (which are ultimately made by VA but based on these IOM reports). This is one of the major issues that was the basis of the RAC's June 19, 2012 "no confidence" report blasting VA's failures of Gulf War veterans.
As another example, Gulf War veterans were successful in getting Congress to include a mandate to VA to contract with IOM to actually conduct an epidemiologic study to determine the prevalence of Multiple Sclerosis (MS) in Gulf War and later veterans. VA continues to break the law and has never to date made that contract with IOM, an issue that has been raised in RAC reports (June 19, 2012) and Congressional hearings, to no avail.
VA's record for Gulf War veterans is pitiful. And when semi-independent bodies like the RAC have raised these and related issues to VA leadership, instead of fixing the underlying problems, VA leaders have chosen to shoot the messengers and sweep the problems under the rug.
Conditions like GERD and MS and many other diagnosed neurologic, respiratory, G-I, skin, and other conditions should be presumptive for all 1991 Gulf War veterans. But without a major shake-up in VA-OPH and elsewhere in VA, coming from the highest levels, it will not improve, and VA will continue to earn a failing "F" grade for Gulf War veterans from nationally acclaimed media analysts.
*RAC June 19, 2012 report: http://www.va.gov/RAC-GWVI/Committee_Documents.asp
*IOM reports: "Gulf War and Health" series, http://www.iom.edu/Reports.aspx?Search=gulf%20war
*March 2013 Congressional hearing: http://veterans.house.gov/hearing/gulf-war-what-kind-of-care-are-veterans-receiving-20-years-later
*Whistleblower reporting example, which affects not just Gulf War but burn pits and so many other deployment health issues, all of which the Deployment Health Working Group, DoD's Force Health Protection office, and VA's Office of Public Health conspire to cover up: http://www.theamericanconservative.com/articles/va-whistleblower-ignites-firestorm-over-vets-illnesses/
EXAMPLE TEXT FROM AN IOM REPORT
"The Committee reported that, in the absence of carefully designed
human studies expressly of sarin's or cyclosarin's long-term health
effects at doses that do not produce acute signs and symptoms, the
Committee concludes that the data remain inadequate or insufficient to
determine whether persistent long-term effects are associated with lowlevel
sarin exposure." --- [Ed. Comment: And thus, there is no presumptive related to sarin or cyclosarin, to which (along with mustard gas) at least 100,000 U.S. troops during the 1991 Gulf War are known to have been exposed ... ]
SOURCE: VA Federal Register posting related to IOM report, archived at http://www.vmwusa.org/index.php?view=article&catid=59%3Agulf-war-illness&id=124%3Ava-denies-presumption-of-service-connection-for-sarin-exposed-gulf-war-vets&format=pdf&option=com_content