Secondary prevention Flashcards
What is secondary prevention?
To reduce the impact of disease or injury, that has already occurred, through early detection and treatment.
What is the aim of secondary prevention?
To improve prognosis
Prevent or slow progression
What methods does secondary prevention use?
Screening, diet, education and exercise
What is screening?
A process of identifying apparently healthy, asymptomatic people who may be at an increased risk of a disease or condition. Early detection of disease, precursor or genetic susceptibility.
What happens if screening identifies a risk?
If identified, further test and treatment follows to reduce the risk of complications arising from the condition.
What is a screening test compared to?
A gold standard diagnostic test that confirms result of screening, producing true and false results, to determine the screening sensitivity and specificity.
What is sensitivity?
How good the screening method is at identifying those with the disease to reduce the number of FALSE -VEs.
What is the calculation for sensitivity?
True +ve / (True +ve + False -ve)
How many true +ves/ cases it can detect
High % shows sensitivity
What is specificity?
How good the screening method is at excluding those without the disease to reduce the number of FALSE +VEs.
What is the calculation for sensitivity?
True -ve / (True -ve + False +ve)
How many true -ve it can detect
High % shows specificity to the disease
How can false results be reduced?
By having a strict criteria for the screening test.
What is the purpose of predicted values?
To show how likely it is that a results is correct.
What is the PPV and what does it show?
PPV = True +ve / (True +ve + False +ve)
A high PPV shows less false +ve results
A low PPV shows high false +ve results
What is the NPV and what does it show?
NPV = True -ve / (True -ve + False -ve)
Shows the chance of not having / being a true -ve.
NPV is usually high
What affects the NPV?
Prevalence - If prevalence of a disease is >90% of a population, NPV will fall as will see more True +ves than -ves.
What is the calculation for prevalence?
True +ve + False -ve / All tested
What is a screening programme?
Screening test plus options available for the Pt when the risk is identified.
What are the risks of screening for each result arm?
True +ve leads to labelling, identifying a disease which has no treatment.
False +ve would cause unnecessary anxiety, fear and cost
False -ve creates false reassurance and causes a delay in intervention
True -ve undergone invasive, time consuming and costly tests.
When will screening for a condition be allowed?
If the condition has an understood timeline with an identified pre-clinical phase in which it is detectable.
There is treatment available that will alter the outcome and has RCT evidence.
Benefits must outweigh the risks.
The disease must be significant, of high prevalence and fatal within a population.
At a reasonable cost.
Have high specificity and sensitivity.
What screening tests are available in UK?
Breast, cervical and colon
What screening tests are available that are non-NSC?
Prostate, chlamydia and vascular risk
What is volunteer bias?
Pts who volunteer and attend screening are more likely to be health conscious and have a healthier lifestyle than those that don’t, lowering their risk of having the disease.
What is lead time bias?
Time between early detection and clinical presentation will appear to be increased and survival time increased, if Pts are detected early, compared to those not screened.
What is length time bias?
Less aggressive diseases have a longer pre-clinical phase and so are more likely to be detected by screening and have a better prognosis.
