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Flashcards in Session 6 Deck (10):

List the criteria for implementing a screening program, including those relating to the condition, the test, the treatment and the programme

Important health problem
Early detectable stage
Epidemiology understood
Simple, safe
Precise, valid
Agreed cut off
Agreed policy on test positives
Evidence based
Proven effectiveness
Benefit should outweigh harm
Quality assurance for whole program


List the advantages and disadvantages of screening for disease

Advantages - potential to give a better outcome compared to finding something in the usual way
Disadvantages - false positives/negatives, alteration of usual doctor/patient contact


Define the term 'diagnosis'

The definitive identification of a suspected disease or defect by application of tests, examinations or other procedures to definitely label people as having or not having a disease


Define the terms 'sensitivity', 'specificity', 'positive predictive value', 'negative predictive value'

Sensitivity - detection rate, disease present, probability a case will test positive
Specificity - disease absent, probability a non-case will test negative
PPV - probability that test positive has the disease (strongly influenced by prevalence)
NPV - proportion of test negatives without the disease


Describe how to calculate sensitivity, specificity, PPV, NPV and prevalence

Sensitivity = true positive/true positive+false positive (a/a+c)
Specificity = true negatives/true negative+false negative (d/d+b)
PPV = true positive/true positive+false positive (a/a+b)
NPV = true negative/true negative+false negative (c/c+d)
Prevalence = true positive+false negative/whole population (a+c/a+b+c+d)


Describe implications of false screening results

False positive - unnecessary worry, put through further tests not needed, turned into patients when they are not ill, lower uptake of screening in the future
False negative - not offered further tests that may have benefits them, disease not diagnosed, falsely reassured, delayed presentation with symptoms in future


Give examples of screening programmes in the UK

Abdominal aortic aneurysm
Bowel cancer (60-69%)
Breast cancer (50-70%)
Cervical cancer
Diabetic retinopathy
Down's syndrome
Fetal anomalies
Sickle cell and thalassaemia
Inherited metabolic diseases


Describe difficulties of evaluating the effectiveness of screening programmes

Must be based on good quality evidence
Lead time bias - early diagnosis falsely appears to prolong survival, but was only diagnosed earlier
Length time bias - detectable diseases more likely to have favourable prognosis
Selection bias - studies skewed by healthy worker effect (RCT would deal with this bias)


Explain sociological critiques of health promotion and screening

Victim blaming - individuals encouraged to take responsibility for own health
Individualising pathology
Individuals and populations subject to surveillance
Prevention part of social control?
Social constructionist:
Health and illness practices seen as moral
Screening targeted more at women than men


Define the term 'screening'

A systematic attempt to detect an unrecognised condition by the application of tests, examinations or other other procedures, which can be applied rapidly (and cheaply) to distinguish between apparently well persons who probably have the disease (or its precursor) and those who probably do not