Block 5: Week 2- Screening Flashcards
List UK Major screening programmes for Antenatal & Newborn
- Down’s Syndrome
- Foetal anomaly USS
- Infectiousdiseasesinpregnancy
- Antenatal Sickle cell & Thalassaemia
- Newborn and Infant Physical Exam
- Newborn Blood spot
- NewbornHearing Screen
Name some of the Adult Major screening programmes
- AAA
- Breast Cancer
- Cervical Cancer
- BowelCancer
- Diabetic Retinopathy
What are the Wilson & Junger Criteria?
Principles of Practice of Screening for Disease
PATHETIC Little Fred
- Policy of who to treat
- Acceptable test
- Treatment exits
- History of disease understood
- Economically balanced
- Test/ Examination exists
- Important health problem
- Case findings should be Continuous Process, not just a once and for all project
- Latent Period
- Facilities for Dx & Tx available
Define Overdiagnosis
Correct diagnosis of a disease but diagnosis is irrelevant because the disease will never cause symptoms within pt’s lifetime
What is Overtreatment?
Unneccessary Tx which does not improve health
What is the Popularity Paradox
The more you overdiagnose people the more popular the screening becomes
Define Sensitivity
Proportion of people who have disease that the test correctly detects
(Likelihood that if you have the disease the test will pick up that you have it & get positive result)
Define Specificity
Proportion of people who do not have the disease that the test correctly identifies as not having the disease
(Likelihood that if you do not have the disease the test will identify you as disease free)
Using Diseae Positive, Disease Negatie, Screening Test positive, Screening Test negative
Draw a table showing how you get: TP, TN, FP, FN
How do you calculate specificity?
TP / (TP+FN)
How do you calculate sensitivity?
TN/ (TN+FP)
Sensitivity & Specificity measure test performace & are ____ of ____ ______ in a population
If you have a disease the senitivity tells you the probability that the test will pick up that disease
BUT: If you test +ve _____ ______ or ____ can tell you the proboabilty that you have the disease. This depends on the disease prevalence
Sensitivity & Specificity measure test performace & are independant of disease prevelance in a population
If you have a disease the senitivity tells you the probability that the test will pick up that disease
BUT: If you test +ve NEITHER sensitivity or specificity can tell you the proboabilty that you have the disease. This depends on the disease prevalence
What is PPV?
(positive predictor value)
Probabilty that person has disease given that they’ve had a +ve result
What is NPV?
The probability that the person doesn’t have the diease given they’ve had a negative result
How do you calculate PPV?
TP/ (TP+FP)
How do you calculate NPV
NPV= TN/ (TN+FN)
What are the types of bias in screening?
- Healthy Screenee
- Lead Time
- Length Time Bias
What is Healthy Screenee Bias?
People that attending screening live longer than those that do not- even if screening is useless
What is the lead time bias?
Screening can detect illness earlier when its more responsive to tx
•HOWEVER, USELESS screening can appear to increase survival time by simply detecting the disease earlier but not actually resulting in longer life (eg: you’ve had the diagnosis for longer so appear to live longer post dx)
What is the length time bias?
- Screening better @ detecting disease the develop slowly
- Slow developing disease means you live longer
- Therefore, screen detected disease likely to have better prognosis even if it results in no difference in tx
Therefore: Longer lasting, less severe vesions of the diease are more likely to be picked up because more severe ones more likely to kill you before screening. Gives the ilusion of better prognosis post screening
