HaDSoc Session 6 Flashcards
What is opportunistic case finding in disease presentation?
Health professional takes opportunity to check for potential conditions on presentation of symptoms for a different disease
What is screening?
Systematic attempt using simple, rapid and cheap tests to detect an unrecognised condition in apparently well people
Describe the process of diagnosis.
Presentation –> Hx, examination and tests –> disease/no disease –> Tx that pt is willing to take risks of due to self-identification of problem
Describe the process of screening.
Rapid, cheap test –> screen +ve = high risk, -ve = low risk –> diagnostic tests if +ve –> disease/no disease –> Tx if necessary
What is the purpose of screening?
Give a better outcome in comparison with spontaneous presentation or opportunistic case finding
What screening and diagnostic tests are used for breast cancer?
Mammography and fine needle aspiration
Who is screened for breast cancer and how often?
50-70 y.o. Females, 3 yearly
What screening and diagnostic tests are used for bowel cancer?
Faecal occult blood test and colonoscopy
What are the screening and diagnostic tests used in AAA?
Single US scan and surgery is appropriate
Who is screened for bowel cancer and how often?
60-69 y.o. Males 2 yearly
What are the advantages of AAA screening?
Decreases risk of death from rupture by ~50%
What are the disadvantages of AAA screening?
Of 238 invited only one would present in the next 10 years, Tx may result in death anyway, reduced QoL with Tx, intolerable anxiety of having untested AAA
Why is there currently no national screening programme for prostate cancer, breast cancer
Could do more harm than good
What disease criteria must be met for a screening programme to be introduced?
Important, epidemiology and natural Hx well understood, early detectable stage, cost-effective primary interventions fully explored
What test criteria must be met for a screening programme to be introduced?
Simple, safe, precise, valid and acceptable to population
What must be known about a test used for screening in order for an agreed cut-off and policy of further investigation to be defined?
Distribution of test values
What is a true +ve screening result?
Disease present and +ve test
What is a false +ve screening test?
Disease absent, +ve test
What is a false -ve screening result?
Disease present and -ve test
How is disease detected?
Spontaneous presentation, opportunistic case finding, screening
What is a true -ve screening result?
Disease absent and -ve test
What are the implications of false +ve screening results?
Undergo stress, anxiety and inconvenience and cause direct and opportunity costs
What are the implications of false -ve test results?
Inappropriately reassured and therefore may delay presentation with symptoms
What is sensitivity?
Detection rate = proportion of people with disease detected, probability of cases test +ve
What does high sensitivity of a screening test mean?
Test good for detecting screened for disease
What is specificity?
Proportion of non-cases that test -ve = probability non-case tests -ve
What does high specificity of a screening test mean?
Tests good at correctly identifying non-cases
What is +ve predictive value?
Probability a +ve test is a case
What is +ve predictive value strongly influenced by?
Prevalence
What effect does low prevalence have of +ve predictive value?
Reduces it
What is -ve predictive value?
Proportion of test -ves that are not cases
Do sensitivity and specificity vary with the population?
No
What treatment criteria must be met for a screening programme to be put in place?
Must have effective EBP for which early implementation is advantageous and clinical management must be optimised in practices before they can participate in screening
What programme criteria must be met for screening to be implemented?
Proven effectiveness, quality assurance, facilities for counselling false +ves and facilities for diagnosis and Tx
Why must the knowledge base be much stronger for screening compared to clinical practice?
Targets apparently healthy people to offer them help for something they may never thought about
What are some of the issues in screening for disease?
Alteration of usual dr-pt contact, complexity of screening programmes, evaluation, limitations of programmes and sociological critiques of programmes
Why are women less than 25 y.o. Not screened for cervical cancer?
It is rare and lesions detected at this stage are likely to regress
What is cervical screening not conducted more frequently in women aged 50-64 y.o.?
Natural Hx means older onset unlikely and will not lead to mortality
When are women aged 65+ screened for cervical cancer?
If they have not been screened since 50 or if there have been recent abnormalities
What process is used in cervical screening?
Speculum –> cervix cell sample –> cells in preservative fluid –> cytology lab interprets and grades
What is lead time bias?
Early diagnosis falsely appears to prolong survival by shifting start-point of known disease so pts love for the same length of time but longer knowing about disease
What is length time bias?
Screening programmes better at picking up slow-growing cases that may never have needed curing
What is selection bias in screening programmes?
Those who engage in screening are more likely to perform health promoting behaviours
How can selection bias be overcome in new screening programmes?
Use of RCTs
What are the limitations of screening programmes?
Screening can reduce risk of disease/complications but not guarantee protection; all programmes have false +ves and -ves; pts need to make an informed choice; uncertainties and extent of over-diagnosis; communicating benefits and risks can be challenging
What are structural critiques of screening programme?
Victim blaming and individualising pathology
What is victim blaming?
Not all individuals are equally able to take responsibility for their own health
What is the problem with individualising pathology in screening?
Suggests we should invest in primary intention more
What are the surveillance critiques of screening?
Individuals and population are more subject to surveillance potentially offering an apparatus of social control
What are the social constructionist critiques of screening?
Health and illness practices moral so give meaning through social relationships e.g. Screening is responsible and needs to be ‘gotten used to’ with non-attendance being deviant or irresponsible
What is the feminist critique of screening?
Targeted more at women than men
What are the Wilson-Junger criteria?
4 criteria screening programmes must meet regarding the disease/condition, the test, treatment and programme
