PSYC 3110 Lecture Notes - Lecture 15: Statistical Hypothesis Testing, Cervical Screening, Hpv Vaccines
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6 Apr 2018
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Lecture 15: Screening
* Next four lectures a mini series on risk
- The idea of risk has been implicit in some of what we have looked at but we haven’t
really looked at issue
- Today we are looking at screening
- What is screening?
Risk
• Key concept in medicine, health promotion, psychology, ... engineering, finance, ...
– Screening & immunization
– Genetic risk
– Risk communication
- Risk found in many different disciplines
- Risk is a huge topic in these different disciplines
- Same word used in different contexts
- Today we are talking about risk in the context of screening
• Complex construct
– Probabilistic
We are talking about phenomenon where the best you can ever do Is that you can get a
degree of certainty
With risk you are talking about probabilities
Screening is all about probabilities
Never a case of if you do a b and c you will never get breast cancer
– Moralistic
What does this mean? Think back to smoking… if smoking increases probability of
getting lung cancer. There is a moral component of smoking. Smoking involves people
making moral judgments
Risk in health is almost always about making moral judgments
There is moral discourse associated with it
– Individualistic vs. Socio-cultural approaches
Psychology tends to use individualistic approach (How does an individual make
decisions based on particular risks or perceptions of risk)
Socio-cultural (how do we as a society look at risk)
- Even when dealing with probability there are different interpretations
- We assume it is straightforward but it is not
- Risk is a quite complex construct
Screening
• Definition
• Rationale
– Health risk management on population level
– Focus on those at higher risk of particular disease
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– Early detection of disease
– Earlier detection = better health outcomes
• Introduction of mass screening
- Idea is that you will save lives with mass screening
• Problems
– Technical implementation
– Reluctance in adoption
– Unexpected negative side effects of participation
Screening is not just a good thing
It has negative side effects that have to be traded off (both individual and population
level)
– Debates about effectiveness of particular forms
- Have to set up clinics. People have to take time off work to attend.
- People knew it would be difficult in terms of technical implementation (funding and
infrastructure). Did not expect reluctance in the population to screening.
- Reluctance a psychological issue
- Screening is a population level health intervention
- Very often people debate when you should start breast cancer screening. 40 vs. 50. If
you as an individual have a need to have a test to check for breast cancer your doctor will
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find more resources at oneclass.com
tell you to. Screening is about population level. Want to find people with risk at a
population level.
- Screening is targeted at where you know the risk is higher. It doesn’t mean if you aren’t
in targeted group you aren’t at risk. The rationale about screening is about catching it in
the high risk groups
- On the whole the rationale is about early detection. The idea is that for many diseases if
you catch them early there are good treatment outcomes. If you don’t there aren’t.
New born screening. The idea for this is that there are particular kinds of conditions
that if you identify them immediately when the child is born you can intervene and have
positive outcomes. If you don’t catch them early it can lead to terrible outcomes.
What is included in what is tested varies across countries and even provinces
Disagreement over what should be included
Is the benefit of the screening on the population level justified on the good it can do?
Effectiveness of Screening
• Highly context dependent
– Invasiveness of screening method
Some are highly invasive others are not
– Statistical prevalence
Screening is a population strategy
There has to be a relatively high prevalence for screening to work and make sense
– Cultural beliefs around disease and interventions
Colon cancer screening
– Economic factors
– Availability of cures
Would you want to know if there was no cure?
– Progression of disease
If you have a disease that progresses rapidly screening may not be effective
- Not effective for all diseases and circumstances
Cancer Screening
• Recommendations: (Vary by jurisdictions
– Pap smears to check for cervical cancer, in women from age 21 to 65
– Mammograms to check for breast cancer, for women after age 40 or 50 to 75 (or later)
– Colon cancer screening, for men and women ages 50 to 75
• Most screening doesn’t prevent cancers, but does prevent deaths
Breast Cancer
• Affects around 1 in 9 women (lifetime risk)
Women at different ages are more or less risk and with different genetic profiles
are at more or less risk
• Canada estimates (2012): 22,700 new diagnoses; 5200 deaths
• Screening motivated by
find more resources at oneclass.com
find more resources at oneclass.com