Cancer Screening Flashcards
What is screening?
A test on a healthy (symptom free) person who does not suspect they have a problem - reduces the risk of future ill health, gives information to patient.
What is screening not?
It does not give a diagnosis, but indicates who is at higher risk and needs further investigation.
What is meant by incidence?
Measure of the probability of the occurrence of a given medical condition in a population within a specified time period.
What is meant by prevalence?
The number of individuals with a condition.
What is meant by validity?
The ability to distinguish between who has the disease and who has not.
What is meant by the number needed to treat?
The number of people needed to be screened to be able to identify one person with the condition.
What is meant by sensitivity?
Ability of the test to correctly identify who has the disease (true positive).
What is meant by specificity?
Ability of the test to correctly identify who does not have the disease (true negative).
What is meant by positive predictive value (PPV)?
The number of people who did have the disease, out of the number of people tested positive.
What is meant by negative predictive value (NPV)?
The number of people who did not have the disease, out of the number of people tested negative.
State 2 biases with screening.
Healthy screening bias - people who come for the disease are healthier than those who don’t come. Lead time bias - apparent survival time for people picked up at an earlier stage of the disease. Length of time bias - screening better at picking up long-lasting conditions rather than slow growing disease.
Why is over-diagnosis bad?
Increases the number of cases of cancer - very indolent tumours detected. It’s very expensive. Patients become worried for no reason.
Who is invited for cervical screening?
Women aged 25 to 64.
State a test done in bowel cancer screening.
Faecal occult blood test. Flexible sigmoidoscopy (narrow tube with a light and tiny camera on one end, called a sigmoidoscope or scope, used to look inside your rectum and lower colon), if high risk full colonoscopy.
State the standard screening for breast cancer.
Women aged 49-70 (who haven’t yet been genetically tested for BRCA-1/2 gene) invited for mammogram every 3 years.
