Screening Flashcards
What is screening
actively identifying disease/pre-disease in apparently health subjects who may benefit from early treatment
What are the criteria for screening to be justified
Condition must be important ie high freq or big impact on individuals
Primary prevention not feasible/effective
There must be an identifiable pre-clinical stage of the disease
There must be a test which separates subjects with a high risk of the disease from subjects with a low risk of the disease
The test must give many true positives/negatives
What screening programmes exist in the UK
Bowel cancer screening for 60-74 yr olds every 2 years
What biases exist in screening
Lead time bias = wanting screened cases to survive longer
Length bias = slow growing tumours detected by screening
Selection bias + overdiagnosis (may never be diagnosed otherwise)