Screening Programmes Flashcards
what is a screening?
a test offered to an asymptomatic person to detect those who have a high probability of having a disease. It is not a diagnostic procedure, those who have a positive test will need further investigation.
what is the purpose of the cervical screening programme?
uses early detection the earlier it it found the less urgent medical attention needed.
what are the 10 stages for early disease detection?
-condition should be an important problem for the individual and the community
-there should be an accepted treatment for the patient with the disease
-facilities for diagnosis and treatment should be available
-there should be a recognisable latent or early stage
-there should be a suitable test or examination
-the test should be acceptable to the population
-the natural history of the condition including development from latent to declared disease, should be understood adequately
-there should be an agreed policy on whom to treat as patients
-the cost of the case finding programme should be economically balanced in relation to expenditure on medical care as a whole
-case finding should be a continuing process
what are the later additions of screening programmes?
-option to opt out
-minimise risks
-promote equity for entire population
-benfits should outweigh harm
what is an underlying cause of cervical cancer?
Human papilloma virus
how does HPV progress to cervical cancer?
-persistent infection can cause changes in cells which for some people will progress to cancer
what are some other risk factors for cervical cancer?
-smoking
-poor immune function
-multiple sexual partners
what is HPV
-a group of DNA viruses
-over 200 types
-80% of people infect it but most clear it
-patients who have persisting infection with a high risk oncogenic
subtype of HPV are at risk of developing pre cancerous changes and cervical cancer
how does the virus enter the cervix?
it is thought that microabrasions in the basement membrane allow it to get into replicating cells. it can enter the cervical epithelia at the transformation zone
where does HPV replicate?
in maturing squamous cells which then turn into koilocytes (mature squamous cells which have noticable cytoplasmic alterations)
what does low risk HPV tend to result in?
free viral DNA within the cell
-responsible for viral warts
how does high risk HPV result in neoplasia?
-they incorporate their DNA into the host cell
-viral E6 and E7 proteins are responsible for reactivating the cell cycle in cells which are not normally proliferating
what does persistent infection and disruption of the cell cycle result in?
proliferation of the epithelial cells without an external stimulus. precursor lesions for cervical cancer. these are termed CIN (Cervical intraepithelial neoplasia) and CGIN (cellular glandular intraepithelial neoplasia)
what are precursor regions?
cervical inreaepithelial neoplasia, divided into CIN1, CIN2, CIN3
what are the high risk subtypes for HPV?
16, 18, 31, 45
