Abstract:
Objective--To determine whether patients suffering from Multiple Chemical Sensitivity Syndrome (MCS) show variations or abnormalities in immunologic parameters distinguishable from the results of similarly tested control subjects.
Design---Case control comparison study.
Participants--Forty-one MCS cases were recruited from the files of a community allergist who cares for a large number of patients with health problems attributed to environmental chemicals. Selection criteria included patients seen between January, 1989 and June, 1990 with diagnoses of chemical sensitivity or formaldehyde sensitivity, and who had symptoms which were at least 3 months duration and which involved at least three organ systems icluding the CNS, and who reported sensitivity to four or more substances. Thirty-four control subjects were recruited from the patient population of the University of Washington Occupational Musculoskeletal Disorders Clinic and the University of Washington Spine Resource Center.
Results--IL-1 generation and CD4 counts showed statistically significant differences between cases and controls. The temporal pattern seen in IL-1 generation suggested that the observed differencces represented testing artifact. CD4 counts were more often categorized as abnormally elevated among cases than controls, and the same pattern was seen in comparisons of groups of cases with high or low MCS severity. A factor of great concern is the degree of discordance between the study lab and the university lab, suggesting that the differences in categorization of CD4 count may represent measurement artifact. Anti-formaldehyde IgG, anti-brush border antibodies, and Ta1 count were abnormal more often among controls than among cases, which appears to be evidence against the immunologic hypothesis. The highest positive predictive value of any test or combination of tests was 68%. and the highest negative predictive value was 60%. Intra-laboratory reproducibility was low for Ta1 count, CD4/CD8 ratio, and IL-1 generation.
Conclusions--The clinical significance of the difference in CD4 counts is unclear. Even if there were a true difference between cases and controls, it would not be possible to tell whether it was a direct effect of chemical exposure, or a result of other factors such as psychological impact of the cases' chronic symptoms. Also, there is no known biologic mechanism which would support a causal relationship between elevated CD4 counts and the types of symptoms commonly experienced by MCS patients. Since their predictive value is low and interpretation of abnormal results is not meaningful, routine use of these immunologic tests to assess MCS is strongly discouraged. It may be worthwhile to investigate further the distribution of immunologic markers in MCS patients, but only in the setting of controlled studies.