Lecture 4, part 5 Flashcards
Definition of length bias
The overrepresentation among screen-detected cases of those with a long preclinical phase of dz and thus a more favorable prognosis
Definition of lead time
The interval between the dx of a dz at screening and when it would have been detected d/t development of sx
Definition of lead time bias
When comparing mortality among screened and unscreened groups, survival may erroneously appear to be increased among screen-detected cases because the dx was made earlier in the course of the dz
Definition of volunteer bias
Ppl who choose to participate in screening programs are likely to be different from those who do not volunteer in a number of ways that affect survival
Tendencies of volunteers for a screening program
Better health
Lower mortality
Better compliance to txs
Volunteers for a screening program may:
Have a FHx of dz
Unhealthy lifestyle
Steps in screening
Screen asymptomatic pop
If likely to have dz, run diagnostic tests
If they have the dz, treat
What to consider in terms of feasibility of a screening program
Convenience
Discomfort level
Risk
Cost
Availability of diagnostic tools/tests
Availability of tx
Screening test can correctly ID individuals who do and do not have the preclinical dz
-Consider possible adverse consequences of false pos/false negs
Reliability definition
Repeatability of a measure over time or between observers/administrators
The percent agreement or consistency btwn multiple observations, measurements, tests, or responses
What are some types of reliability measures?
Inter-observer
Intra-observer
Respondent
Inter-test
Definition of inter-observer reliability
Reliability between 2 or more observers
Definition of intra-observer reliability
Reliability btwn readings made by the same observer at different times
Definition of respondent reliability
Reliability between 2 different tests on the same cases
Definition of inter-test reliability
Reliability that involves repeat responses to the same question by the same individuals to different interviewers
Definition of validity
Test or instrument’s ability to measure what it intends to measure
