Interventions for Health
Promotion
1. Screening
Amer Eltwati Ben Irhuma,*
Abstract:
As
a method of preclinical secondary prevention, screening is the rapid
administration of a simple test to distinguish individuals who may have a
condition from those who probably do not have a condition. It can be an
effective, efficient tool in preventive health care if used for conditions applicable
to the screening model and directed toward an at-risk population. A unique
characteristic and significant advantage of screening is that it can be applied
to individuals and groups.
Three
questions provide a means of analyzing the screen ability of a disease:
1. Is the
condition significant?
2. Can
screening for the condition be done?
3. Should
screening for the condition be done?
Screening
programs are not appropriate for all conditions or all communities. Alternative
methods of reaching the desired health outcome should always be considered.
Screening in health care presents numerous roles for health care workers and
provides them with a valuable preventive tool in the care of healthy
individuals.
Keywords:
screening, prevention, health care, disease.
Introduction:
Screening
has received growing recognition as a valuable tool for health care
professionals, particularly as health care delivery moves toward preventive
interventions. The primary objective of
screening is the detection of a disease in its early stages, to treat it and
defer its progression. The basic assumption guiding this process is that detection
during the early asymptomatic period allows treatment at a time when the course
of the disease can be altered significantly. The screening concept is based on
the principle that disease is preceded by a period of asymptomatic pathogenesis
(disease development) when risk factors predisposing a person to the
pathological condition are building momentum toward manifestation of the
disease. Screening takes advantage of the early pathogenic state. The
administration of tests during this stage identifies specific variables that
distinguish individuals who most likely have the condition from those do not.
Screening is not considered a diagnostic measure; it is seen as a preliminary
step to direct a health care provider in assessment of the ostensibly healthy individual’s
chances of becoming unhealthy. The ultimate goal could be curative, but more
often it is to prevent further development of the disease or to ameliorate the
possible outcomes. A second, but equally important, objective of screening is
to reduce the costs of managing the disease by avoiding the more vigorous
interventions required during its later stages. The added attraction of a
cost-conscious approach to health care mandates that health care professionals
at all levels acquire a basic understanding of the screening process and its
application.
Advantages and the Disadvantages of Screening:
Preclinical
illness and previously unrecognized disease in individuals may be detected via screening
efforts.1-4 Screening tests offer several advantages. They are often
simple, and frequently a trained technician administers them. The simplicity of
the screening procedure decreases the time and cost of involved health care
personnel and enables less skilled technician to administer the test. This also
reduces cost and permits the more appropriate use of highly skilled costly
professionals at the definite, diagnostic tests.
A
second advantage is the ability to apply the screening process to both
individuals and large groups. In an individual screening program, one person is
tested by a health professional who has designated the individual as high. The practitioner
can make this selection independently, the
health care agency
can
*) Professor of Surgery and Dean Faculty of Medicine, University of Sebha , Libya
define
a specific policy, or a legislation body can require the screening body law as
in the case of phenylketonuria (PKU) or lead-screening programs. Group or mass
screening occurs when a target population is selected on the basis of an
increased incidence of a condition or a recognized element of high risk within
the group. An example of this would be lower–income populations or cultural
groups that exhibit a significant prevalence of a particular condition, such as
hypertension.
A
third advantage is the ability to provide one-test specific screening or
multiple test screenings. A one-test disease-specific screening is the
administration of a single test that searches for a characteristic that indicates
a high risk of developing a disorder. An
example of this would be blood pressure screening to evaluate the risk of
hypertension. Multiple test screening is the administration of two or more
tests to detect more than one disease. In some cases, one sample can be used to
evaluate the possibility of several conditions, saving time and money and
making the process efficient and economical. For example, a blood sample can be
evaluated for both elevated glucose and cholesterol levels. Ultimately, the
combination of the relatively low cost and flexibility of a screening test
makes screening adaptable to all levels of the health care delivery system.
The
disadvantage of screening stem largely from the imperfection of modern science,
which results in a margin of error for most instruments and tests. When program
effectiveness depends on the test’s
ability to distinguish those who probably do have the disease from those who do
not, the margin of error can precipitate
serious consequences. Some individuals who do not have the condition will be
referred for further tests and some who do have the disease will not. Those
incorrectly referred suffer needless anxiety while awaiting more definitive
diagnostic procedures. The must also
bear the burden of the cost, follow-up visits, lost time, and inconvenience.
The
effects on those whose disorders have been missed are even more important.
These individuals leave with a false sense of a healthful state that will be
shattered eventually, and they lose the opportunity to receive early treatment
that could prevent irreversible damage. The difficulty of balancing the
benefits to some against the losses to others in an ethical issue of most
screening programs. The significance of this disadvantage can vary; therefore,
it should be assessed for each project, disease, and population.
Selection of a Screenable Disease:
The
selection of a screenable disease goes beyond examination of the disease alone.
The selection process must also encompass less tangible factors, such as the
emotional and financial impact of the disease’s detection on the screened
population. Even after gathering data and reviewing the critical issues, the
final decision to screen or not to screen must often be reached with incomplete
evidence or with answers that raise ethical issues. The potential uncertainties
confounding the decision emphasize the need to conduct an exhaustive analysis
of available material to obtain a decision that is as objective and scientific
as possible. The answers to the following three questions provide a basis for
designating a disease as screenable or not screenable:
1. Does
the significance of the disorder warrants consideration as a community problem?
2. Can the
disease be detected by screening?
3. Should
screening for the disease be done?
As
simplistic as these questions may appear, the answers or lack of answers may
expose numerous complex issues that determine whether or not a well-informed
decision can be made on screenability.
Significance:
The
significance of a disease refers to the level of priority assigned to the
disease as a public health concern. Although the opinions of political and
public interest groups may enter into the evaluation, significance generally is
determined by the quantity and quality of life affected by the disorder. The
greater the physical and psychological harm experienced by the population, the
greater is the need to designate the disease as a priority health problem. The
first step in assigning screenability is evaluation of this significance to
decide if the disorder warrants the time, effort, and funds that must be
allocated. Estimating the quality of life affected by a disease presents a
problem. The perception of quality is subjective and individual evaluations may
differ. For example, not all people equally perceive the disability resulting
from a disease; some make adjustments and cope, whereas others do not. Those
who do not would be more likely to say that the quality of their lives is significantly
lower than that of the people around them.5-7
By
contrast, measures of the quantity of life affected by the disease are more
readily obtainable. Disease-specific mortality rates present one picture of
this effect, whereas prevalence and incidence rates provide another. Prevalence
is the proportion of existing cases during a specific time; incidence is the
frequency of new cases during a specified period.8 Usually chronic
conditions are measured by their prevalence, whereas acute conditions are
assessed by their incidence.
In
this area of cost-conscious health care, a new dimension has been added to the
evaluation of significance: the cost required to treat the disease. In some
cases the prevalence of the disorder may not be great, but the problem requires
disproportionate amounts spent on maintenance or management after the condition
is fully expressed. For example, with PKU the incidence is not significant, but
the cost of a case undetected at birth is a lifetime of case management. Given
the costly outcome if undetected and the reasonable price of the test itself,
the cost of screening all newborns is nominal.
Can the Disease Be Detected by Screening?
With
the relative significance of the disease established, the next step is to
determine if health professionals can screen for the disease. Do
well-documented diagnostic criteria for the disorder exist? .to support a
screening program?
Diagnostic Criteria:
Detection
of a disease requires knowledge of characteristics that indicate its presence
or, as in screening, its early pathogenic, asymptomatic state. Selected diagnostic criteria should be well
documented; they should not be merely accepted or commonly used indicators. The
impact of uncertainty in detecting disease is amplified when considering the
application of the screening design. Some diseases, such as sickle cell anemia,
are defined by the presence or absence of a single, isolated factor. Other
conditions, such hypertension, are indicated by the measurement of
statistically derived numerical values for which a normal range has been set.
Disagreement over the parameters of the normal range, combined with contentions
that what is abnormal for one individual may not be abnormal for another, make
these conditions more controversial to designate as screenable diseases.
Screening Instruments:
The
next step is to determine if methods exist to detect the disease during early
pathogenesis. If instruments are available, a careful analysis should determine
if any of them fulfill the requirements for the screening process: safe,
cost-effective, and accurate. Ultimately the question is how well the
instrument can distinguish those individuals who probably do not have and will
not develop the condition from those who are likely to develop it. The
variables that aid in instrument evaluation include reliability and validity.
Reliability:
Reliability
is an assessment of the reproducibility of the test’s results when different
individuals with the same level of skill perform the test during different
periods and under different conditions. If the same result emerges when two
individuals perform the test, inter-observer reliability is shown. If the same
individual is able to reproduce the results several times, intra-observer
reliability is shown. Therefore testing for instrument reliability can yield
data on the accuracy and quality of the test.9
Validity:
Validity
reflects the test’s ability to distinguish correctly between diseased and
non-diseased individuals, or the accuracy of the test.7,10 In a
controlled setting, validity is evaluated by testing the instrument on a group of individuals who have positive
or negative results. The ideal result is to have the
instrument pick out 100% of the disease people (positive e reactions) and 100%
of the nondiseased people (negative reactions). Such accuracy rarely occurs in
practice; therefore, the measure of validity has been divided into two
components that quantify the margin of error in the screening instrument.
Sensitivity
measures the first component. This refers to the proportion of people with a
condition who correctly test positive when screened. A test with poor
sensitivity will miss individuals with the condition and there will be a large
number of false-negative test results; individuals actually have the condition
but were told they are disease free.
Specificity
measures the test’s ability to recognize negative reactions of non-diseased
individuals. A test with poor specificity will result in false-positive test
results. Individuals with false-positive test results are told that they have a
condition when in actuality they do not.
The
issues emerging from investigation of the screening instrument demonstrate the
significant influence it has on the entire process. Data on the reliability and
validity of the test and screening
programs in general provide valuable information
to evaluate anticipate, and ideally control these influences , enabling the
program to work effectively toward its goal.
Community Resources:
Implementing
a screening program depends on availability of appropriate community resources,
such as funds, health care workers, follow-through, treatment resources, and
administrative personnel. Judicious organization of the overall programs key to
its success. Knowledge of the disease’s
characteristics and the screening instrument are useless without financial and
organized human support to apply it. The overall approach is complex, requiring
intense efforts in the area of partnership development.
A
lead agency is identified to oversee the development process of the community
health program. For the lead agency to
develop and develop a screening program, partnerships are essential. The agency
must contact and organize necessary stakeholders. Examples of stakeholders include key
community organizations including houses of workshop, community centers,
schools, transportation agencies, and volunteer organizations. Key community
individuals are those who are considered leaders within the community.
Should Screening for the Disease Be Done?
After
determining that the disease is significant and can be screened for,
establishing whether health professionals should do so is the final step.
Screening for a particular disorder and ultimately treating those with the
early-identified disorder should improve the chances of a favorable outcome in
comparison with those whose disorder is not found until signs and symptoms
become evident. Therefore, several questions must be considered. If a test is
accurate in the identification of a condition in the early stages, is there any
benefit to the individual? Are there effective treatment modalities for the
condition?
Interventions and Treatment Modalities:
Screening
is based on the disease’s asymptomatic period; therefore, adequate information
must exist concerning (1) the optimal time for screening, (2) specific
intervention during this time, and (3) knowledge as to the effect of early
detection and treatment on the prognosis. Without this knowledge, health care
professionals are unable to explain how the consequences of the detected disease
differ from those undetected. They can neither evaluate nor explain the health
benefits derived from the screening program.
Not
intervening can be almost as detrimental as the adverse effects of a disorder.
In this situation, not only has the program misled the screened population that
has a health benefit will result from their efforts, but the development and
implementation of the screening program has used both personal and community
resources that can not possibly alter the course of a particular disease.
Follow-
up is critical to determine if
intervention strategies prescribed are in fact taking place. The prescribed
regimen may be very broad and include a wide variety of intervention strategies
such as diet, exercise, and drug therapy. Follow up may include an evaluation
and review of the literature that discusses evidence-based practice pertaining
to a particular drug, as well as identification of intervention characteristics
that impair follow-up, such as cost, inconvenience, or side effects. Safety of
the intervention is a concern when considering the widespread application of a
remedy after a screening program. Risks or harmful side effects can be costly
in terms of human health and the increased medical care required to correct the
iatrogenic effects resulting from the intervention. Health care professionals
must decide if these risks significantly diminish the success of the treatment
and outweigh the benefits derived from the treatment.
References:
1.
Anderson, E. & Mc Farlane J. Community as partner: Theory and practice in
nursing. New York
1.2. American Cancer Society. Colorectal cancer:
early detection. http://www.cance.
org/docroot/home/index.asp. 2000.
3.
Centers for Disease Control and Prevention. Lead fact sheet. 2004.
http//www.cdc.gov/ exposureport/2nd/lead-factsheet.htm.
1.4. Centers for Disease Control and Prevention.
The adult blood lead level epidemiology and surveillance program. 2004. Http://
www.cdc.gov.niosh/ablesh.html.
5.
National Cancer Institute. Prostate cancer: Screening and testing. 2004 http://www.
nci.nih.gov/cancerinfo/screening/prostate.
6.
U.S. Institute
of Health
7.
Sackett, D., Straus, S., Richardson NEW York
8.
Lundy, K. & Janes, S. Community health nursing: Caring for the public’s
health. Boston
9.
Polit, D., Beck, C., & Hungler, B. Essentials of nursing research: Methods, appraisal, and Utilization. New York
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U.S. Baltimore
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