Reanalysis or Secondary Use of Data

Reanalysis or Secondary Use of Data

Surveillance for a health problem can use data originally collected for other purposes — a practice known as the reanalysis or secondary use of data. This approach is efficient but can suffer from a lack of timeliness, or it can lack sufficient detail to address the problem under surveillance. Because the primary collection of data for surveillance is time-consuming and resource-intensive if done well, it should be undertaken only if the health problem is of high priority and no other adequate source of data exists.

Table 5.4 Types of Registries and Examples of Selected Types

1. Vital event registration a. Birth registration b. Marriage and divorce registration

c. Death registration 2. Registries used in preventive medicine a. Immunization registries b. Registries of persons at risk for selected conditions

c. Registries of persons positive for genetic conditions 3. Disease-specific registries a. Blind registries b. Birth defects registries

c. Cancer registries d. Psychiatric case registries e. Ischemic heart disease registries

4. Treatment registries a. Radiotherapy registries b. Follow-up registries for detection of iatrogenic thyroid disease

5. After-treatment registries a. Handicapped children b. Disabled persons

6. Registries of persons at risk or exposed a. Children at high risk for developing a health problem b. Occupational hazards registries

c. Medical hazards registries d. Older persons or chronically ill registries e. Atomic bomb survivors (Japan)

f. World Trade Center survivors (New York City) 7. Skills and resources registries 8. Prospective research studies

9. Specific information registries Adapted from: Koo D, Wingo P, Rothwell C. Health Statistics from Notifications,

Registration Systems, and Registries. In: Friedman D, Parrish RG, Hunter E (editors). Health Statistics: Shaping Policy and Practice to Improve the Population’s Health. New York: Oxford University Press; 2005, p. 91. Weddell JM. Registers and registries: a review. Int J Epid 1973;2:221–8.

Exercise 5.2

State funding for a childhood asthma program has just become available. To initiate surveillance for childhood asthma, the staff is reviewing different

sources of data on asthma. Discuss the advantages and disadvantages of the following sources of data and methods for conducting surveillance for asthma. (Figure 5.12 in Appendix C indicates national data for these different sources.)

• Self-reported asthma prevalence and asthmatic attacks obtained by a telephone survey

of the general population. • Asthma-associated outpatient visits obtained from periodic surveys of local health-care

providers, including emergency departments and hospital outpatient clinics.

Check your answers on page 5-58

Major health data systems Data regarding the characteristics of diseases and injuries are

critical for guiding efforts for preventing and controlling those diseases. Multiple systems exist in the United States to gather such data, as well as other health-related data, at national, state, and local levels. These systems provide the “morbidity and mortality reports and other relevant data” for surveillance, as described by Langmuir, and examples of such systems are listed in Appendix E. Remember, however, that surveillance is an activity — the continued watchfulness over a disease by using data collected about it — and not the data about a disease or the different data systems used to collect or manage such data.

Surveillance for communicable diseases principally relies upon reports of notifiable diseases from health-care providers and laboratories and the registration of deaths. Because the most common use of surveillance for communicable diseases at the local level is to prevent or control cases of disease, local surveillance relies on finding individual cases of disease through notifications or, where more complete reporting is required, actively contacting

health-care facilities or providers on a regular basis. 10 At the state and national level, the principal notification system in the United

States is the National Notifiable Disease Surveillance System (NNDSS). State and local vital registration provides data for monitoring deaths from certain infectious diseases (e.g., influenza and AIDS).

More About the National Notifiable Disease Surveillance System

A notifiable disease is one for which regular, frequent, and timely information regarding individual cases is considered necessary for preventing and controlling the disease.

The list of nationally notifiable diseases is revised periodically. For example, a disease might be added to the list as a new pathogen emerges, and diseases are deleted as incidence declines. Public health officials at state health departments and CDC collaborate in determining which diseases should be nationally notifiable. The Council of State and Territorial Epidemiologists, with input from CDC, makes recommendations annually for additions and deletions. However, reporting of nationally notifiable diseases to CDC by the states is voluntary. Reporting is mandated (i.e., by legislation or regulation) only at the state and local levels. Thus, the list of diseases considered notifiable varies slightly by state. All states typically report diseases for which the patients must be quarantined (i.e., cholera, plague, and yellow fever) in compliance with the World Health Organization's International Health Regulations.

Data in the National Notifiable Disease Surveillance System (NNDSS) are derived primarily from reports transmitted to CDC by the 50 states, two cities, and five territorial health departments.

Source: National Notifiable Diseases Surveillance System [Internet]. Atlanta: CDC [updated 2006 Jan 13]. Available from: http://www.cdc.gov/osels/ph_surveillance/nndss/nndsshis.htm .

Surveillance for chronic diseases usually relies upon health-care– related data (e.g., hospital discharges, surveys of the public, and mortality data from the vital statistics system). Given the slow rate of change in the incidence and prevalence of these diseases, data for surveillance of chronic conditions need not be as timely as those for acute infectious diseases.

Surveillance for behaviors that influence health and for other markers for health (e.g., smoking, blood pressure, and serum cholesterol) is accomplished by population surveys, which might

be supplemented with health-care related data. The Behavioral Risk Factor Surveillance System (BRFSS), the Youth Risk Behavior Surveillance System (YRBSS), the National Health Interview Survey (NHIS), and the National Household Survey on Drug Abuse are all surveys that gather data regarding behaviors that influence health. The National Health and Nutrition Examination Survey (NHANES), probably the most comprehensive survey in the United States of health and the factors that influence it, gathers extensive data on physiologic and biochemical measures of the population and on the presence of chemicals among the population resulting from environmental exposures (e.g., lead, pesticides, and cotinine from secondhand smoke). Data from NHANES have been used for approximately 40 years to monitor the lead burden among the general public, demonstrating its marked elevation and then substantial decline after the mandated removal of lead from gasoline and paint.

Exercise 5.3

Assume you work in a state in which none of the following conditions is on the state list of notifiable diseases. For each condition, list at least one

existing source of data that you need for conducting surveillance on the condition. What factors make the selected source or data system more appropriate than another?

Listeriosis: A serious infection can result from eating food contaminated with the bacterium Listeria monocytogenes. The disease affects primarily pregnant women, newborns, and adults with weakened immune systems. A person with listeriosis has fever, muscle aches, and sometimes gastrointestinal symptoms (e.g., nausea or diarrhea). If infection spreads to the nervous system, such symptoms as headache, stiff neck, confusion, loss of balance, or convulsions can occur. Infected pregnant women might experience only a mild influenza-like illness; however, infections during pregnancy can lead to miscarriage or stillbirth, premature delivery, or infection of the newborn. In the United States, approximately 800 cases of listeriosis are reported each year. Of those with serious illness, 15% die; newborns and immunocompromised persons are at greatest risk for serious illness and death.

Spinal cord injury: Approximately 11,000 persons sustain a spinal cord injury (SCI) each year in the United States, and 200,000 persons in the United States live with a disability related to an SCI. More than half of the persons who sustain SCIs are aged 15–29 years. The leading cause of SCI varies by age. Motor vehicle crashes are the leading cause of SCIs among persons aged <65 years. Among persons aged ≥65 years, falls cause the majority of spinal cord injuries. Sports and recreation activities cause an estimated 18% of spinal cord injuries.

Lung cancer among nonsmokers: A usually fatal cancer of the lung can occur in a person who has never smoked. An estimated 10%–15% of lung cancer cases occur among nonsmokers, and this type of cancer appears to be more common among women and persons of East Asian ancestry.

Check your answers on page 5-60