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Summary of Notifiable Diseases
United States 2003
Interpreting Data
Incidence data in the Summary are presented by the date of report to CDC as determined by the MMWR week and year assigned by the state or territorial health department. In addition, data in the Summary are reported by the state in which the patient resided at the time of diagnosis. For many of the nationally notifiable infectious diseases, surveillance data are independently reported to various CDC programs. Thus, surveillance data reported by other CDC programs might vary from data reported in the Summary because of differences in 1) the date used to aggregate data (e.g., date of report or date of disease occurrence), 2) the timing of reports, 3) the source of the data, 4) surveillance case definitions, and 5) policies regarding case jurisdiction (i.e., which state should report the case to CDC).
The data reported in the Summary are useful for analyzing disease trends and determining relative disease burdens. However, these data must be interpreted in light of reporting practices. Disease reporting is likely incomplete, and completeness might vary depending on the disease. The degree of completeness of data reporting might be influenced by the diagnostic facilities available; control measures in effect; public awareness of a specific disease; and interests, resources, and priorities of state and local officials responsible for disease control and public health surveillance. Finally, factors such as changes in methods for public health surveillance, introduction of new diagnostic tests, or discovery of new disease entities can cause changes in disease reporting that are independent of the true incidence of disease.
Public health surveillance data are published for selected racial and ethnic populations because these variables can be risk markers for certain notifiable diseases. Race and ethnicity data also can be used to highlight populations for focused prevention efforts. However, caution must be used when drawing conclusions from reported race and ethnicity data. Different racial/ethnic populations might have different patterns of access to health care, potentially resulting in data that are not representative of actual disease incidence among specific racial/ethnic populations. Surveillance data reported to NNDSS are in either individual case-specific form or summary form (i.e., aggregated data for a group of cases). Summary data often lack demographic information (e.g., race); therefore, the demographic-specific incidence rates presented in the Summary might be underestimated.
In addition, not all race and ethnicity data are collected uniformly for all diseases. For example, certain disease programs collect data on race and ethnicity by using one or two variables, based on the 1977 standards for collecting such data issued by the Office of Management and the Budget (OMB). However, beginning in 2003, certain CDC programs, including the tuberculosis program, implemented OMB’s 1997 revised standards for collecting such data; these programs collect data on multiple races per person by using multiple race variables. Additionally, although the recommended standard for classifying a person’s race or ethnicity is based on self-reporting, this procedure might not always be followed.
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