Community Medicine and Screening Techniques
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Questions and Answers

What is screening?

Screening is the search for unrecognized disease by means of rapidly applied tests, examination or other procedures in apparently healthy individuals.

What is the aim of screening?

Screening aims to detect early disease (in apparently healthy persons) before it becomes symptomatic.

Is screening test a final diagnosis?

False

What are the differences between a Screening test and a Diagnostic test? (Select all that apply)

<p>Diagnostic test results are used as a basis for treatment</p> Signup and view all the answers

What are the uses of screening? (Select all that apply)

<p>Control of diseases</p> Signup and view all the answers

Which of the following are types of screening? (Select all that apply)

<p>High risk or selective screening</p> Signup and view all the answers

What does mass screening mean?

<p>Means the screening of a whole population. For example, night blood smear examination for microfilaria of every individual in hyper-endemic areas of filariasis.</p> Signup and view all the answers

What does high risk or selective screening mean?

<p>Diseases tend to be aggregated in the family, so screening of other family members leads to a detection of additional cases. E.g. diabetes, hypertension, and breast cancer.</p> Signup and view all the answers

What does multi-phasic screening mean?

<p>The application of two or more screening tests in combination to a large number of people at one time is better than to carry out a separate screening test for a single disease.</p> Signup and view all the answers

What does opportunistic and case finding screening mean?

<p>The common characteristic of case finding is that it is usually done as part of a clinical encounter for some other health condition.</p> Signup and view all the answers

What are the characteristics of a good screening test? (Select all that apply)

<p>Readily available</p> Signup and view all the answers

Which of the following are WHO criteria for diseases to be screened for? (Select all that apply)

<p>The cost of case-finding (including a diagnosis and treatment of patients diagnosed) should be economically balanced</p> Signup and view all the answers

A screening test should be reliable

<p>True</p> Signup and view all the answers

What kind of variations affect the screening test? (Select all that apply)

<p>Observer variations</p> Signup and view all the answers

Which of the following are components of a validity screening test? (Select all that apply)

<p>Sensitivity</p> Signup and view all the answers

What is sensitivity in a screening test?

<p>Sensitivity is the ability of a test to correctly identify those having the disease; i.e. true positives. It is the percentage of diseased persons showing the test result positive.</p> Signup and view all the answers

What is predictive value of a test?

<p>Predictive value of a test means the diagnostic power of a test.</p> Signup and view all the answers

What does predictive value of a positive test mean?

<p>Predictive value of a positive test refers to the probability of an individual really having the disease, if the test result is positive (i.e. percentage of positives probably having the disease).</p> Signup and view all the answers

What does false positive mean?

<p>False positive means those who do not have the disease but the test result is positive. It's the percentage of non diseased persons wrongly identified as having the disease, because the test result is positive.</p> Signup and view all the answers

What does prevalence of the disease mean?

<p>The prevalence of a disease is the proportion of individuals in a population who have the disease at a specific point in time.</p> Signup and view all the answers

Study Notes

Community Medicine

  • Community medicine is a branch of medicine focusing on health of populations.
  • Dr. Esra Abdeen is the presenter, with relevant qualifications.

Screening

  • Screening is a searching method to find unrecognized diseases in supposedly healthy individuals, through tests, examinations or procedures.
  • The goal of screening is to find diseases early, before symptoms appear. This is an important preventative approach.
  • Screening tests identify groups to undergo testing.
  • Diagnostic tests apply to individual patients, and aim for accuracy and use in treatment.

Uses of Screening

  • Case detection
  • Disease control
  • Research
  • Educational purposes

Types of Screening

  • Mass screening - examines entire population (e.g. blood smear for filariasis, but needs treatment and follow-up).
  • High-risk/selective screening - targets groups at higher risk (e.g., diabetes in family members).
  • Multi-phasic screening - uses multiple tests at once (more than one at a time is better)
  • Opportunistic and case finding screening - part of a clinical encounter for other health conditions.

Characteristics of a Good Screening Test

  • Simple
  • Readily available
  • Safe to use
  • Quick to administer
  • Inexpensive
  • Treatment plan available if positive
  • Acceptable to the population

Screening Test Criteria - (WHO Hill Criteria)

  • The condition should be an important public health issue.
  • A recognizable latent or early symptomatic phase should exist.
  • The condition's natural history should be understood.
  • Effective and acceptable treatments should be available.
  • The screening test should be acceptable to the population.
  • Diagnosis and treatment facilities should be accessible.
  • The cost of finding cases, diagnosis and treating the patients should be balanced economically.

Screening Test Reliability

  • Reliability (repeatable/reproducible)
    • Observer variation (intra/inter-observer)
      • Intra-observer variation- same person, different times
      • Inter-observer variation- different people, same time
    • Biological variation - changes in an individual (e.g., pulse, respiratory rate).
    • Mechanical variation - errors caused by machines or procedures. Solutions include checking machines/procedures.

Screening Test Validity

  • Validity (accuracy) - correctly identifying those with the disease from those without.
    • Example: glucose tolerance test is better than a urine test for sugar.
  • Valid tests have two main components:
    • Sensitivity- correctly identifying those with the disease.
    • Specificity- correctly identifying those without the disease.

Predictive Value of a Test

  • Diagnostic power of a test (positive/negative test results)
    • Predicitive value of a positive test- probability a person has the disease if the test is positive (a/a+b x 100%)
    • Predicitive value of a negative test- probability a person does not have the disease if the test is negative (d/c+d x 100%).
  • False positives - when a person without the disease tests positive
  • False negatives - when a person with the disease tests negative

Prevalence

  • Prevalence of a disease = a+c / a+b+c+d (measures how common a disease is)

Exercise and Answer

  • An example exercise using numbers to showcase the calculations (sensitivity, Specificity, predictive value).
  • The answer to this exercise with all the calculations and diagnosis, presented in table format.

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Related Documents

Lecture Screening PDF

Description

This quiz explores the principles of community medicine, focusing on the importance of screening in detecting diseases early. Learn about the different types of screening, their uses, and how they contribute to public health. Dr. Esra Abdeen provides insights into the key methodologies utilized in this field.

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