preventative medicine and screening Flashcards
what is secondary prevention?
it is actions to detect the disease early to prevent the emergence of symptoms and complications - prophylactic treatment and screening for asymptomatic disease
what is screening?
it is the testing of a population for a condition who do not have recognised symptoms
what is the difference between a screening and diagnostic test?
screening offers individuals information as to whether they are high or low risk. If they are high then they are offered a diagnostic test to see if they have the condition or not
what are current UK screening programmes?
bowel, breast and cervical cancer, AAA, diabetic eye, foetal anomaly and infectious disease in pregnancy, newborn and infant physical, newborn hearing and blood spot and sickle cell and thalassaemia
what are advantages of screening?
can make decisions about health, early treatment which can be more effective, reduced development and mortality and can detect problems before are noticed
what is AAA?
it is an enlargement of the abdominal aorta and weakening of the artery wall
what are risk factors for AAA?
smoking, diabetes, high blood pressure and high cholesterol
what is the epidemiology for AAA?
most common in men over 65 and 5000 deaths per annum in UK
what is the screening for AAA?
it is offered to men over 65 and is a non invasive USS. It has led to a 50% reduction in deaths over ten years
what are disadvantages of screening?
not 100% accurate
false positives - anxiety, overtreatment and harmful procedures
false negative - false reassurance and no treatment
can lead to difficult decisions
who decides what screening is done?
The UK screening committee (criteria)
what is the criteria for screening?
economically balanced in relation to medical care as a whole
benefits outweigh harm
important health condition as judged by frequency and severity
intervention available
socially, clinically and ethically acceptable to health professionals and public
simple, safe, precise and validated
reduces morbidity/mortality
why was the prostate screening removed?
cannot differentiate between slow and fast growing cancer
treatment had significant risk
around 85% of positives were false
around 15% of negatives were false
cannot therefore be justified in low risk populations
what is down syndrome?
it is caused by the addition of chromosome 21 - trisomy 21. It is associated with learning disability and other severe health conditions and occurs in 1 in 700 live births
what is the screening for down syndrome?
every pregnant women offered test from 10-14 weeks of pregnancy - diagnostic that gives a 0.5% chance of miscarriage
what are the rules for abortion around down syndrome?
termination of pregnancy is legal until term
what are the ethics around screening?
cost effectiveness, benefit vs harm, risk and severity, prevention, effective intervention and morbidity
what is sensitivity?
the proportion of people with a disease that are identified as having the disease with a positive test result
what is specificity?
the proportion of people without a disease who are correctly reassured by a negative result of a test
what is the positive predictive value?
the probability that a person with a positive test result has the disease
what is the negative predictive value?
it is the probability that a person with a negative result does not actually have the disease
what is DCIS?
ductal carcinoma in situ
what is the issue with screening?
it is not clear the extent to which diagnosis and treatment of DCIS may prevent the occurrence of invasive breast cancer in the future
what did Duffy et al 2016 study show?
the ecological study showed that for every 3 screen-detected cases of DCIS, in the next 3 years there was one fewer invasive cancer results
what is a true positive and false positive?
true - screen detects and is actually there, false - screen protects and is not actually present
what is a false and true negative?
false - the screen says there is no disease but there is
true - no disease on screen and actually no disease
what is the sensitivity calculation?
true positive/(true positive+false negative)
what is the specificity calculation?
true negative/ (true negative+ false positive)
what is the calculation for PPV?
true positive/(true positive+false positive )
what is the calculation for NPV?
true negative/(true negative + false negative )
