Cancer Screening And Prevention Flashcards
Define sensitivity
Whether the test has the ability to identify that the positive results are actually positive
How good the test is at picking the disease up
Define specificity
The ability of the test to correctly identify those who have negative results are actually negative of the disease
Positive predictive value
Probability that those with a positive screening test actually have the disease
Negative predictive values
Probability that those with a negative screening test do not have the disease
What us screening
Investigations of asymptomatic people in order to classify them as likely or unlikely to have the disease
What happens after a positive result
Further tests are done to determine a diagnosis
Those with a positive diagnosis are treated
Prerequisites for screening
Test needs to be suitable
Relatively inexpensive
Natural history of the disease needs to be known
Disease needs to have a latent period no clinical symptoms but is detectable
Needs to be suitable treatment facilities available
Treatment needs to be relatively inexpensive
Agreed policy on who to treat
Cost economically balanced in relation to cost of medical care as a whole
Case funding needs to be continuous and not a one off
When are diseases classed a suitable for screening
Common and has severe consequences
Must have a preclinical phase undiagnosed but detectable
Early treatment must offer some advantage over later treatment
Screening evidence of net benefit
What is lead time bias
Successful screening detects disease in preclinical phase so the period between detection and death could therefore be longer simply because we have observed the process for longer not increasing the lifetime of that patient in comparison to a patient who was detected in the clinical phase of treatment
Needs to be accounted for when comparing survival between those screened and unscreened
What is length bias
Those diseases which can be Identified by screening are more likely to be less aggressive than those who are not detected when screened
More aggressive disease not likely to be detected as it can develop between screening times
What we bp the cancers screened for in England
Breast cancer
Bowel cancer
Cervical cancer
Breast screening
Every 3 years for women between the ages of 47-73
This group is invited
Over request
Criticisms of breast cancer screening
Since the introduction of screening the number of ductal carcinoma in situ have increased this condition not palpable
It accounts for 20% of breast cancers
Criticism is that these lesions may never progress and affect the women life and treatment can include mastectomy for a disease which may have never needed treatment
How many of those called back actually have breast cancer
1 in 6
What likely interventions related to improve breast cancer screening attendance
Simple friendly comprehensive infor available
Out of hours appointments
Provision of transport
One to one follow up of non attendees to address anxieties or concerns
