Screening Flashcards
what are some screening programmes for adults?
\+ abdominal aortic aneurysm (AAA) \+ bowel cancer \+ breast cancer \+ cervical cancer \+ diabetic retinopathy
what are some screening programmes for pregnancy?
+ foetal anomaly
+ infectious diseases
+ sickle cell and thalassemia
what are some screening programmes for newborns and infants?
+ physical examination
+ blood spot
+ hearing
what are the factors used in deciding if a condition can be screened for?
+ important public health problem
+ natural history understood
+ recognisable latent or early symptomatic phase
what is sensitivity?
how well the test picks up having the disease:
no. of results where disease detected in people with disease / no. people with disease x 100
what is specificity?
how well the test detects not having the disease:
no. of normal results where disease is not detected in people without disease / no. people without disease x 100
what are features of a highly sensitive test?
+ picks up most of the disease
+ very few false negatives
what are features of a highly specific test?
+ correctly detects no disease
+ very few false positives
what is positive predictive value?
how reliable is the test result which shows disease present
what is a negative predictive value?
how reliable is the test result showing disease is NOT present
what are advantages of screening?
\+ reduced disease incidence \+ reduced disease mortality \+ earlier, less radical treatment \+ cost-effective \+ overall population benefit
what are possible disadvantages of screening?
\+ false reassurance \+ over-investigation and treatment \+ anxiety \+ longer period of morbidity with unaltered prognosis \+ harm from screening test \+ opportunity costs
what are some biases in screening programmes?
+ participant (volunteer) bias
+ lead-time bias
+ length-time bias
what is lead-time bias?
length of time between the detection of a disease (usually based on new, experimental criteria) and its usual clinical presentation and diagnosis (based on traditional criteria)
what is length-time bias?
detection of less aggressive forms of condition in screening
