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Medical surveillance is undertaken to identify changes
in the distributions of diseases in order to prevent or control
these conditions within a population.
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A comparison of incidence rates across populations can help
to determine characteristics of populations at higher (and lower)
risk.
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Surveillance of deaths is convenient because the information
is virtually complete, standardized and inexpensive to obtain. Nevertheless,
data collected from death certificates may be limited by omitted
or inaccurate information.
- Age adjustment is used to remove the influence of any age
differences when comparing the disease frequencies of two populations.
- Premature death measures the years of potential life lost
to a particular disease, and therefore weighs most heavily deaths
that occur at young ages.
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A 68-year-old female retired office manager presented with a
dry, hacking cough of several months’ duration. She reported
a history of smoking one pack of cigarettes per day for the past
30 years. To evaluate the patient’s cough, her family physician
ordered a chest x-ray, which was unremarkable except for an increased
density in the hilum (midcentral portion) of the lung fields. A
sputum specimen was collected, and abnormally-appearing cells were
noted on microscopic evaluation. Because these cells suggested a
malignancy, a bronchoscopic examination was performed to allow direct
visualization of the large airways. A partially obstructing mass
was visible at the distal end of the right main stem bronchus. Brushings
from this mass revealed cells consistent with a diagnosis of squamous
cell carcinoma. Other diagnostic studies indicated that the cancer
had spread to involve the brain and bones. Radiation therapy was
administered to all sites of cancer involvement. Nevertheless, the
patient’s condition rapidly deteriorated, and she died
less than 6 months after diagnosis.
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In this chapter, attention is focused on one of the most basic
functions of epidemiology:
detection of
the occurrence of health-related events or exposures in a target
population.
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The goal of this detection, or surveillance, is
to identify changes in the distributions of diseases in order to
prevent or control these diseases within a population. The term
surveillance literally means “to watch over,” and
traditionally medical surveillance activities were developed to
monitor the spread of infectious diseases through a population.
Today, however, surveillance programs have been applied to a wide
variety of other conditions, such as congenital malformations, injuries,
occupational health problems, and cancer, as well as other behaviors
that affect health. Regardless of the type of outcome under consideration,
medical surveillance activities involve the following key features:
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- 1. Continuous data collection
and evaluation
- 2. An identified target population
(such as a community, a work force, or a group of patients)
- 3. A standard definition of
the outcome of interest
- 4. Emphasis on timeliness of
collection and dissemination of information
- 5. Use of data for purposes
of investigation or disease control.
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The goals of medical surveillance depend on the state of knowledge
about the causes of the condition of ...