Session 6 Flashcards
List the criteria for implementing a screening program, including those relating to the condition, the test, the treatment and the programme
Disease/condition: Important health problem Early detectable stage Epidemiology understood Test: Simple, safe Precise, valid Acceptable Agreed cut off Agreed policy on test positives Treatment: Advantageous Evidence based Program: 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 PKU 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
Structural:
Victim blaming - individuals encouraged to take responsibility for own health
Individualising pathology
Surveillance:
Individuals and populations subject to surveillance
Prevention part of social control?
Social constructionist:
Health and illness practices seen as moral
Feminist:
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
