Full text of study
In response to community concerns about multiple sclerosis (MS) in Texas, the Agency for Toxic Substances and Disease Registry (ATSDR) provided funding to the Texas Department of State Health Services (DSHS) to conduct a pilot surveillance project for MS in a 19-county area of North Texas. The principal goals were (1) to determine the sex-, age-, race- and ethnic-specific prevalence estimates for MS in Texas and (2) to reanalyze the Mesita Elementary School cohort cluster investigation in El Paso, Texas using Texas-specific prevalence estimates.
The primary data source for case ascertainment was medical records from the offices of private neurologists practicing in the 19-county study area and the Texas Tech University Medical Center. Death certificates were used as a secondary source of case ascertainment. Records of patients who resided in the 19-county study area at any time between January 1, 1998 and December 31, 2000 and who had a documented office visit to a neurologist during that time period were considered eligible for inclusion in the study. Demographic and diagnostic information was abstracted from the medical records by project staff. The project neurologist using the Poser criteria for MS confirmed case status. Definite and probable MS cases were used as the numerator and the year 2000 census counts were used as the denominator in the calculation of prevalence estimates.
The results of this project represent the first Texas-specific population-based MS prevalence estimates, including the first MS prevalence estimates for Hispanics and Blacks in Texas. The prevalence estimate for the 19-county study area of 42.8/100,000 (n=182 "definite" and "probable" MS cases) is half that reported for the entire United States in the NHIS data of 85/100,000. The prevalence estimate for non-Hispanic whites is the highest for any of the race/ethnic groups at 56.0/100,000 (95% CI 47.1 - 66.1) followed by non-Hispanic Blacks at 22.1/100,000 (95% CI 8.1 - 48.1), and Hispanics at 11.2/100,000 (95% CI 6.4 - 18.2). The proportion of MS cases among Blacks and non-Hispanic whites for Texas is similar to that reported nationally with the prevalence among whites approximately twice that of Blacks. However, the actual prevalence estimates for both non-Hispanic whites and Blacks in Texas are approximately half that reported nationally. There are no estimates for Hispanics included in the NHIS data that would allow comparison of the Texas data. The lack of information on Hispanic prevalence represents an important data gap.
The findings from the El Paso MS cluster investigation also were re-evaluated. Using the prevalence estimates from the 19-county pilot project, the revised standardized morbidity ratio (SMR) for the Mesita cohort is 8.2 (95% CI 4.5 - 13.8). The SMR for females is 7.1 (95% CI 3.4 - 13.1) and for males the SMR is 13.3 (95% CI 3.6 - 34.1). The original risk estimate that used the 1989-1994 National Institute of Health Survey data was 1.93 (95% CI = 1.06 - 3.24).
The results from this project underscore the need for additional epidemiologic information regarding the distribution of MS in the other areas of Texas and the United States, as well as information on the underlying etiology of the disease. As is illustrated by the revised risk estimate for the El Paso Mesita Elementary cohort, the results of this pilot surveillance project also highlight the need for timely and region-specific prevalence estimates for evaluating MS cluster concerns.
Combined with project results from other areas of the country, the Texas surveillance data will contribute significantly to the current national prevalence estimates of the disease. Notably, Texas also will be able to provide much needed data for the Hispanic population; a population for which almost no information is available. Data generated by projects such as this one will allow DSHS and other health departments to respond to community concerns in a timely and efficacious manner and to begin to address etiologic concerns about the disease.