screening

Question 1

what is the phases of the natural history of disease

Answer 1

underlying
susceptible
subclinical
recovery/disability/death

Question 2

what is primordial prevention

Answer 2

targets the population rather than individuals
focuses on social and environmental intervential
targets conditions that would lead to disease onset

Question 3

what is primary prevention

Answer 3

targets susceptible populations of individual
prevent a disease from emerging and targets healthy individuals
reduces exposure to risk factors

Question 4

what is secondary prevention

Answer 4

targets individuals with subclinical disease
early detection
screening programs

Question 5

what is tertiary prevention

Answer 5

targets clinical and outcome stages of the disease
reduce disease severity and associated complications

Question 6

what is quaternary prevention

Answer 6

Measures taken to identify patients at risk of over-medicalisation
Targets are patients with illness but no disease
Prevents harmful medical interventions

Question 7

what are the disadvantages of classification systems

Answer 7

Classification systems are imperfect
Overlap between different types of prevention, and interventions may fall into more than one category
How can smoking cessation fall into primary, secondary and tertiary prevention?
Is all screening secondary prevention, or can some be classified as primary prevention?

Question 8

what is screening

Answer 8

Screening is the presumptive identification of unrecognized disease or defect by the application of tests, examinations, or other procedures which can be applied rapidly.

Question 9

what are the principles of screenings

Answer 9

1. The condition should be an important health problem.
2. There should be an accepted treatment for patients with recognized diseases.
3. Facilities for diagnosis and treatment should be available.
4. There should be a recognizable latent or early symptomatic phase.
5. There should be a suitable test or examination.
6. The test should be acceptable to the population.
7. The natural history of the condition should be adequately understood.
8. There should be an agreed policy on whom to treat as patients.
9. The cost of case-finding should be economically balanced
10. Case-finding should be a continuous process

Question 10

what is the purpose of a screening test

Answer 10

detect potential disease indictators

Question 11

what is the purpose of diagnostic tests

Answer 11

establish presence/absence of disease

Question 12

what is the target population of screening tests

Answer 12

Large numbers of asymptomatic, but potentially at risk individuals

Question 13

what is the target population of diagnostic test

Answer 13

Symptomatic individuals to establish diagnosis, or asymptomatic individuals with a positive screening test

Question 14

what is the test method of screening tests

Answer 14

Simple, acceptable to patients and staff, should not be harmful

Question 15

what is the test method of diagnostic test

Answer 15

maybe invasive, expensive but justifiable as necessary to establish diagnosis

Question 16

what is the positive result threshold of a screening test

Answer 16

Generally chosen towards high sensitivity not to miss potential disease

Question 17

what is the positive result threshold of a diagnostic test

Answer 17

Chosen towards high specificity (true negatives). More weight given to accuracy and precision than to patient acceptability

Question 18

what is the postive result of a screening test

Answer 18

Essentially indicates suspicion of disease that warrants confirmation

Question 19

what is the positive result of a diagnostic test

Answer 19

Result provides a definite diagnosis

Question 20

what is the cost of a screening test

Answer 20

Cheap

Question 21

what is the cost of a diagnostic test

Answer 21

higher costs

Question 22

what are the aims of screening

Answer 22

To reduce mortality by early detection and early treatment of a condition
To reduce the incidence of a condition by identifying and treating its precursors
To reduce the severity of a condition by identifying people with the condition and offering effective treatment
To increase choice by identifying conditions or risk factors at an early stage in a life-course when more options are available

Question 23

what are the screening steps

Answer 23

identify the population eligible for screening
invitation and information
testing
referral of screen positives and reporting of screen-negative results
diagnosis
intervention, treatment and follow-up
reporting of outcomes

Question 24

what is population-based screening

Answer 24

Systematically screen every person within a population

Question 25

what is selective screening

Answer 25

Applied to a particular subset of the population, e.g. high-risk group

Question 26

what is multiphasic screening

Answer 26

more than one test is applied for more than one condition

Question 27

what is opportunistic screening

Answer 27

during routine healthcare visists

Question 28

what does the national screening committee do

Answer 28

advises ministers in the 4 UK countries on implementing, continuing and modifying population-based screening programmes considers all the evidence and makes recommendations based on a set of criteria that have evolved from the Wilson Jungner criteria

Question 29

what does public health england do

Answer 29

advises on implementation of safe, high quality screening programmes in England develops standards and provides services that help the local NHS implement and run screening services consistently across the country

Question 30

what does UKHSA do

Answer 30

is responsible for planning, preventing and responding to external health threats, and providing intellectual, scientific and operational leadership at national and local level, as well as on the global stage Is an executive agency sponsored by the Department of Health and Social Care

Question 31

what is sensitivity

Answer 31

Proportion of true positives that are correctly identified by the test

Question 32

what is specificity

Answer 32

Proportion of true negatives that are correctly identified by the test

Question 33

what is accuracy

Answer 33

Proportion of true positives and true negatives that are correctly identified by the test

Question 34

what is a true positive

Answer 34

when predicted class and true class is positive

Question 35

what is a false negative

Answer 35

when the predicted class is positive but the true class is negative

Question 36

what is a false negative

Answer 36

when the predicted class is negative but the true class is positive

Question 37

what is a true negative

Answer 37

when the predicted class and true class are negative

Question 38

how do you calculate sensitivity

Answer 38

TP / (TP+FN)

Question 39

how do you calculate specificity

Answer 39

TN / (FP+TN)

Question 40

How do you calculate the positive predictive value PPV

Answer 40

TP / (TP+FP) or

Question 41

How do you calculate the negative predictive value NPV

Answer 41

TN / (FN+TN)

Question 42

How do you calculate accuracy

Answer 42

(TP+TN) / (TP+FP+FN+TN)

Question 43

what does a high sensitivity mean

Answer 43

Most people with the condition have been identified If a test is negative, there is a high degree of certainty that the test subject does not have the disease If a test is positive, the test subject may or may not have the disease

Question 44

what does a high specificity mean

Answer 44

Most test subjects with a positive test do have the disease If the test positive, there is a high degree of certainty that the test subject does have the disease If the test negative, the test subject may or may not have the disease

Question 45

what does the PPV tell us

Answer 45

if a test result is positive, what is the probability that the person has the condition?

Question 46

what does NPV tell us

Answer 46

if a test result is negative, what is the probability that the person does not have the disease?