LHCs that is the basis of the World Health Organization’s classification system for these neoplasms.

On the basis of its evaluation of veterans, occupational, and environmental studies, the committee assigned each health outcome to one of four categories of relative certainty of association with exposure to the herbicides that were used in Vietnam or to any of their components or contaminants (with no intention of specifying particular chemicals). Changes made by the current committee to the categorizations determined by the committee for Update 2008 (as presented in Table 1-1) are noted in boldface in Table 12-1.

The terminology of “early-onset transient peripheral neuropathy” was adopted in Update 2004 as a replacement for the terminology of “acute and subacute peripheral neuropathy” used in Update 1996. Update 1996, the first VAO report to find “limited or suggestive evidence of association” with exposure to the chemicals of interest for this health outcome, also noted in the body of the report that this was a “transient” effect. When US Department of Veterans Affairs (VA) declared this outcome to be presumptively associated with service in Vietnam, its definition included the temporal constraints that symptoms develop within weeks or months of exposure to an herbicide and resolve within 2 years of the date of onset (VA, 1996; see Note 2 at end of Final Rule). Thus, currently qualifying cases are contingent upon when symptoms arise relative to when exposure occurred and that the symptoms are transitory in nature, with recent claims being extremely unlikely. A thorough review of the existing literature in populations with members experiencing early-onset peripheral neuropathy, however, indicates that some individuals continue to manifest neuropathy symptoms long after external exposure has ceased, demonstrating that early-onset peripheral neuropathy is not necessarily a transient condition. Based on this literature, the committee elected to delete the word transient to recognize that symptoms of early-onset peripheral neuropathy may be protracted and recovery from those symptoms may be incomplete. The changes to the classifications made since the previous update are bolded here in Table 12-1 and in Table S-1 in the Summary.

Although VA did not find hypertension to be presumptively related to service in Vietnam (VA, 2010), on the basis of the total weight of available evidence, the current committee reaffirmed the conclusion of the committees for Update 2006 and for Update 2008 to categorize hypertension as having limited/suggestive evidence of association.

As mandated by Public Law (PL) 102-4, the distinctions among categories are based on statistical association, not on strict causality. The committee was directed to review the scientific data, not to recommend VA policy; therefore, conclusions reported in Table 12-1 are not intended to imply or suggest policy decisions. The conclusions are related to associations between exposure and outcomes in human populations, not to the likelihood that any individual’s health problem is associated with or caused by the chemicals in question.

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