SCREENING IN DISEASE CONTROL Flashcards
SCREENING
•_______________ of unrecognized disease or defect by ____________, ________ or other procedures
Presumptive identification
application of tests, examinations
SCREENING
• Is in the _______ level of prevention. For early _________ and ________
second
detection and treatment
Rationale for screening
–___________ will lead to better treatment
early diagnosis
Screening
• To sort out individuals who ____________________ from ______________
probably have the disease
Those who do not
Screening is intended to be diagnostic
T/F
Not intended to be diagnostic
In screening, Those who test positive are sent for ____________ to ___________
further evaluation to determine whether they do have the disease.
Benefits of screening
• Results used to estimate __________ of a condition in a given population
• Detect disease in individuals who are ___________
• Usefull where you have ______ medical facilities. As it can cover _________________
prevalence
apparently well
poor; large proportion of community
Criteria for mass screening of population
• Disease must be an __________________ problem- prevalence, consequence
• There should be an _________________ for patients with recognized disease.
• Treatment given before symptoms should _____________ than that given after symptoms develop.
• Facilities for __________ and _______ should be available
• Should be early recognizable pre symptomatic stage of disease
important public health
acceptable treatment
reduce morbidity and mortality
diagnosis and treatment
criteria for mass screening of population
• Should be suitable test that is ________ and ______ to the population
•_______________ of the disease should be understood
• there Should be agreed policy on ________________
•Cost of screening should ___________________ when disease is detected
• Screening should be a _______ exercise
acceptable and easy to administer
Natural history
whom to treat as a patient
not outweigh cost of providing medical care
continuous
Criteria for evaluating performance of screening test
• ________
• ________
• ___________
Reliability
• Validity
• Yield
Reliability
Ability of test to yield _____________________________ (______________)
consistent results when performed more than once under the same set of conditions.
repeatability
Reliability
Influenced by ;
1. Lack of _________ of instruments
- Lack of ___________ which results from observer(s) usually due to ________________ procedures and definitions
precision
objectivity
un- standardized
reliability
Influenced by:
- Lack of __________ – characteristic being measurement has changed.
- Lack of ___________ – due to use of different instruments or test kits. Different results n same person
constancy
congruency
Validity
Ability of test to ___________________
measure the characteristic we intend to measure
Validity
- Sensitivity- the ability of the test to yield _________ results in individuals (with or without?) the disease
- Specificity – the ability of test to yield _________ results in individuals (with or without?) the disease
positive ; with
negative ; without
Validity
• Sensitivity = (___________)* 100
• Specificity = (___________) *100
• a = TP (True positive)
• b= FP (False positive)
• c= FN (False Negative)
• d= TN (True Negative)
a /a +c
d/b +d
validity
• A test which is highly sensitive will have (low or high?) false negative result
• A test which is highly specific will give (low or high ?) false positive results
Low
Low
Yield
• Amount of _______________ which is identified as a result of screening
previously unrecognised disease
Yield
Yield affected by
1. _________
2. Prevalence of _________ disease
3. _________ of _________ screening
4. _________________ of population
Sensitivity
Prevalence of preclinical disease
Extent of previous screening
Health behaviour of population
Combination of tests
• Combine different test to have _______________________ in test
• Can combine test in ———- or test in ________
high degree of confidence
series
parallel
Combination of tests
Series – don’t consider individual positive unless _____________. This helps to _________
• Parallel – all administered __________ and person __________________ is considered positive
positive in series of tests
reduce FP.
at same time
with positive result on any
Evaluation of screening programmes
• Use __________,_________ and _______ study designs
• ___________ – cost effectiveness, diagnosis and treatment of those who test positive, yield
• _________ to population -time, comfort
•_________ value – measures whether or not an individual actually has the disease given the results of the screening tests
descriptive , analytical and experimental
Feasibility
Acceptability
Predictive
Evaluation
• Positive predictive value- probability that a person ____________ given that ________________. Shows the proportion of positive results that are ________
• Negative predictive value - Proportion of negative results that are ___________.
actually has the disease
he or she tests positive; truly positive.
truly negative
Evaluation
• Positive predictive value
____/_________ =(a/a+b)
• Negative predictive value -
___/_________= (d/c+d)
TP/TP+FP
TN/TN+FN
evaluation
• Effectiveness-reduction in ____________
morbidity and mortality
evaluation
• Lead time –interval between the ____________________ and when ___________________________
diagnosis of a disease at screening
it would have been detected due to development of symptoms
