Download Screening

Screening
Dr Poonam R Naik
Professor
Department of Community Medicine
Iceberg phenomena of disease
Spectrum of disease
Concept of screening
Active search for disease among apparently
healthy people
Definition: Search for unrecognized disease or
defect by means of rapidly applied tests,
examination or other procedures in
apparently healthy individuals.
Screening vs diagnostic test
Screening Test
Diagnostic test
Apparently healthy
Those with indications
Applied to groups
Applied to single patient
Single criterion
Multiple criteria of
evaluation
Less accurate
More accurate
Less expensive
More expensive
Not a basis for treatment
Basis for treatment
Initiative by: Investigator
Initiative by: Patients
Concept of lead time
Detection programmes: Time lag between
disease onset and usual time of diagnosis:
Long Time lag
Critical points
Early detection before usual time of diagnosis:
Treatment should be successful
Lead Time: Advantage gained by screening:
Period between diagnosis by early detection
and diagnosis by other means
Programme benefits: Terms of its outcome
Aims and objectives of screening
Those who are likely to have the disease or are
at increased risk of the disease under study
Apparently abnormal: Medical supervision
and treatment
Apparently Normal: Periodic screening
Terms
Screening: Who are not seeking health care:
Blood donors: HIV Testing
Case Finding: Who are seeking health care for
other reasons: HIV Testing among Tuberculosis
patients
Diagnostic test: To confirm or refute a
diagnosis
Uses of screening
1. Case detection: Prescriptive screening.
People are screened for their own benefit.
Initiate the treatment appropriately.
Example: Pregnant women
2. Disease control: Prospective screening
For the benefit of others.
Early diagnosis: Effective treatment and
implementation of control measures to
prevent the spread
3. Research Purposes:
4. Educational opportunities: To the
community
Types of Screening
1. Mass screening: Should be backed up by
support measures
2. High risk or selective screening: Screening for
risk factors. Thereby implement control
measures and thus effective.
3. Multiphasic screening: Application of two or
more screening test in combination to a
large group people. Expensive.
Criteria for screening
1. Important public health problem (High
prevalence)
2. Recognizable latent or early asymptomatic
stage
3. Understanding of the natural history of the
diseases
4. Availability of test to detect before the onset
of signs and symptoms
5. Availability of confirmatory tests
6. Effective treatment
7. Agreement on cut off criteria for treatment
consideration
8. Expected benefits (Life saving should exceed
the cost and risks involved)
Think Time
1. Paraphrase screening
2. Enumerate 4 differences between screening
test and diagnostic test
3. Lead time concept: Discuss in view of
diseases with small and long time gap
4. Correct the error:
HIV testing in all antenatal women is an example
of screening
5. Enumerate the types of screening
6. 3 uses of screening