PHC 6001 Screening in Public Health
Practice
What is screening?
-allows for early detection of disease
-followed by clinical diagnosis and treatment
-useful if early detection will improve treatment outcomes
primary type of prevention
-intervention with healthy person before pathological onset of disease
-goal of preventing them from ever getting disease
secondary type of prevention
-intervention in a person who has a disease, but is asymptomatic (preclinical).
screening programs, glucose testing.
tertiary type of prevention
-reduces the impact of disease in someone who is clinically ill, rehab and quick
treatment. relies on available treatment
which diseases can be screened?
- more effective if it is:
cost effective, doesn't hurt too much and isn't too risky, acceptable to the
population, valid and reliable
example: colonoscopy
reliability
you can administer the test moer than once and it will give the same result for an
individual
False Positives
-when a test indicates someone has a disease but they actually don't.
, -unnecessary treatment. may be a stigma that could last beyond the corrected test
result.
false negatives
when the test indicates someone does not have the disease but they actually do
- failure to treat the disease. opt to not change lifestyle and not make plans they
wouldve made if they knew they had the disease
-potential spread of disease
What is sensitivity?
the probability that the test will correctly identify a person with a disease as being
positive
-identifying true positives
sensitivity calculation
number of individuals with pre-clinical disease WHO TEST POSITIVE / number of
individuals with pre-clinical disease x 100
- 2x2 table: TP/TP+FN
a/a+c
Specificity
the probability that the test will correctly identify a person without disease as
being negative
specificity calculation
number of individuals without pre-clinical disease who test negative / number of
individuals without pre-clinical disease x100
-identifying true negatives
-2x2 table: TN/TN+FP
d/d+b
Predictive Value Positive (PVP)
tells us what proportion of patients who screen positive TRULY HAVE disease
Practice
What is screening?
-allows for early detection of disease
-followed by clinical diagnosis and treatment
-useful if early detection will improve treatment outcomes
primary type of prevention
-intervention with healthy person before pathological onset of disease
-goal of preventing them from ever getting disease
secondary type of prevention
-intervention in a person who has a disease, but is asymptomatic (preclinical).
screening programs, glucose testing.
tertiary type of prevention
-reduces the impact of disease in someone who is clinically ill, rehab and quick
treatment. relies on available treatment
which diseases can be screened?
- more effective if it is:
cost effective, doesn't hurt too much and isn't too risky, acceptable to the
population, valid and reliable
example: colonoscopy
reliability
you can administer the test moer than once and it will give the same result for an
individual
False Positives
-when a test indicates someone has a disease but they actually don't.
, -unnecessary treatment. may be a stigma that could last beyond the corrected test
result.
false negatives
when the test indicates someone does not have the disease but they actually do
- failure to treat the disease. opt to not change lifestyle and not make plans they
wouldve made if they knew they had the disease
-potential spread of disease
What is sensitivity?
the probability that the test will correctly identify a person with a disease as being
positive
-identifying true positives
sensitivity calculation
number of individuals with pre-clinical disease WHO TEST POSITIVE / number of
individuals with pre-clinical disease x 100
- 2x2 table: TP/TP+FN
a/a+c
Specificity
the probability that the test will correctly identify a person without disease as
being negative
specificity calculation
number of individuals without pre-clinical disease who test negative / number of
individuals without pre-clinical disease x100
-identifying true negatives
-2x2 table: TN/TN+FP
d/d+b
Predictive Value Positive (PVP)
tells us what proportion of patients who screen positive TRULY HAVE disease
