Identifying or Collecting Data for Surveillance

Identifying or Collecting Data for Surveillance

After the problem for surveillance has been identified and defined and the needs and scope determined, available reports and other relevant data should be located that can be used to conduct surveillance. These reports and data are gathered for different purposes from multiple sources by using selected methods. Data might be collected initially to serve health-related purposes, whereas data might later serve administrative, legal, political, or economic purposes. Examples of the former include collecting data from death certificates regarding the cause and circumstances of death and collecting data from national health surveys regarding health-related behaviors; examples of the latter include collecting data on cigarette and alcohol sales and administrative data generated from the reimbursement of health-care providers.

Before describing available local and national data resources for surveillance, understanding the principal sources and methods of obtaining data about health problems is helpful. As you recall from Lesson 1, the majority of diseases have a characteristic natural history. An understanding of the natural history of a disease is critical to conducting surveillance for that disease because someone — either the patient or a health-care provider — must recognize, or diagnose, the disease and create a record of its existence for it to be identified and counted for surveillance. For diseases that cause severe illness or death (e.g., lung cancer or rabies), the likelihood that the disease will be diagnosed and recorded by a health-care provider is high. For diseases that produce limited or no symptoms in the majority of those affected, the likelihood that the disease will be recognized is low. Certain diseases fall between these extremes. The characteristics and natural history of a disease determine how best to conduct

surveillance for that disease.

Sources and Methods for Gathering Data

Examples of documentation of financial, legal, and

Data collected for health-related purposes typically come from

administrative activities that

three sources, individual persons, the environment, and health-care

might be used for surveillance

providers and facilities. Moreover, data collected for nonhealth–

• Receipts for cigarette and other tobacco product sales.

related purposes (e.g., taxes, sales, or administrative data) might

also be used for surveillance of health-related problems. Because a

• Automated reports of

pharmaceutical sales.

researcher might wish to calculate rates of disease, information

• Electronic records of billing

about the size of the population under surveillance and its

and payment for health-care services.

geographic distribution are also helpful. Table 5.2 summarizes

health and nonhealth-related sources of data, and the box to the left

• Laws and regulations related

to drug use.

provides examples of nonhealth-related data that can be used for surveillance of specific health problems.

Table 5.2 Typical Sources of Data

Individual persons

Health-care providers, facilities, and records • Physician offices • Hospitals • Outpatient departments • Emergency departments • Inpatient settings • Laboratories

Environmental conditions • Air • Water • Animal vectors

Administrative actions

Financial transactions • Sales of goods and services • Taxation

Legal actions

Laws and regulations

A limited number of methods are used to collect the majority of health-related data, including environmental monitoring, surveys, notifications, and registries. These methods can be further characterized by the approach used to obtain information from the sources described previously. For example, the method of collecting information might be an annual population survey that uses an in-person interview and a standardized questionnaire for obtaining data from women aged 18–45 years; or the method might

be a notification that requires completion and submission of a form by health-care providers about occurrences of specific diseases that they see in their practices.

Depending on the situation, these methods might be used to obtain information about a sample of a population or events or about all members of the population or all occurrences of a specific event (e.g., birth or death). Information might be collected continuously, periodically, or for a defined period, depending on the need. Careful consideration of the objectives of surveillance for a particular disease and a thorough understanding of the advantages and disadvantages of different sources and methods for gathering data are critical in deciding what data are needed for surveillance and the most appropriate sources and methods for obtaining it. 9,14 We now discuss each of these four methods.

Environmental Monitoring

Monitoring the environment is critical for ensuring that it is

Examples of environmental monitoring

healthy and safe (see Examples of Environmental Monitoring).

Multiple qualitative and quantitative approaches are used to

• Cities and states monitor

air pollutants.

monitor the environment, depending on the problem, setting, and

• Cities and towns monitor

planned use of the monitoring data.

public water supplies for bacterial and chemical contaminants.

Survey

• State and local health

A survey is an investigation that uses a “structured and systematic

authorities monitor beaches, lakes, and

gathering of information” from a sample of “a population of

15 swimming pools for

interest to describe the population in quantitative terms.” The

increased levels of

majority of surveys gather information from a representative

harmful bacteria and

sample of a population so that the results of the survey can be

other biologic and chemical hazards.

generalized to the entire population. Surveys are probably the most

common method used for gathering information about populations.

• Health agencies monitor

animal and insect

The subjects of a survey can be members of the general public,

vectors for the presence

patients, health-care providers, or organizations. Although their

of viruses and parasites that are harmful to

topics might vary widely, surveys are typically designed to obtain

humans.

specific information about a population and can be conducted once

• National, state, and local

or on a periodic basis.

departments of transportation monitor roads, highways, and

Notification

bridges to ensure that

A notification is the reporting of certain diseases or other health-

they are safe for traffic; they also monitor traffic

related conditions by a specific group, as specified by law,

regulation, or agreement. Notifications are typically made to the

to ensure that speed

limits and other traffic

state or local health agency. Notifications are often used for

laws are observed.

surveillance, and they aid in the timely control of specific health

• Public safety and health departments periodically

problems or hazardous conditions. When reporting is required by

law, the diseases or conditions to be reported are known as

monitor compliance with

laws requiring seat belt

notifiable diseases or conditions.

use. • Occupational health authorities monitor noise

Individual notifiable disease case reports are considered

confidential and are not available for public inspection. In most

levels in the workplace

to prevent hearing loss

states, a case report from a physician or hospital is sent to the local

among employees.

health department, which has primary responsibility for taking appropriate action. The local health department then forwards a

copy of the case report to the state health department. In states that have no local health departments or in which the state heath department has primary responsibility for collecting and investigating case reports, initial case reports go directly to the state health department. In some states all laboratory reports are sent to the state health department, which informs the local health department responsible for following up with the physician.

This form of data collection, in which health-care providers send reports to a health department on the basis of a known set of rules and regulations, is called passive surveillance (provider-initiated). Less commonly, health department staff may contact healthcare providers to solicit reports. This active surveillance (health department- initiated) is usually limited to specific diseases over a limited period of time, such as after a community exposure or during an outbreak.

Table 5.3 shows the types of notification and examples.

Table 5.3 Types of Notification and Examples

1. Disease or hazard-specific notifications a. Communicable diseases i. World Health Organization: International health regulations require reporting of cholera, plague, and yellow fever ii. National: United States and Canada specify diseases that require notification by all states and provinces, respectively iii. Provincial, state, or subnational: for example, coccidioidomycosis in California b. Chemical and physical hazards in the environment i. Childhood lead poisoning ii. Occupational hazards iii. Firearm-related injury

iv. Consumer product-related injury 2. Notifications related to treatment administration a. Adverse effect of drugs or medical products b. Adverse effect from vaccines

3. Notifications related to persons at risk a. Elevated blood lead among adults b. Elevated blood lead among children

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. 82.

Use of sentinel sites has become the preferred approach

for human immunodeficiency virus/acquired immunodeficiency syndrome (HIV/AIDS) surveillance for certain countries where national population-based surveillance for HIV infection is not feasible. This approach is based on periodic serologic surveys conducted at selected sites with well-defined population subgroups (e.g., prenatal clinics). Under this strategy, health officials define the population subgroups and the regions to study and then identify health-care facilities serving those populations that are capable and willing to participate. These facilities then conduct serologic surveys at least annually to provide statistically valid estimates of HIV prevalence.

Because underreporting is common for certain diseases, an alternative to traditional reporting is sentinel reporting, which relies on a prearranged sample of health-care providers who agree to report all cases of certain conditions. These sentinel providers are clinics, hospitals, or physicians who are likely to observe cases of the condition of interest. The network of physicians reporting influenza-like illness, as described in one of the examples in

Appendix C, is an example of surveillance that uses sentinel

providers. Although the sample used in sentinel surveillance might not be representative of the entire population, reporting is probably consistent over time because the sample is stable and the participants are committed to providing high-quality data.