W 8 Flashcards
Can we reach 100% or 0% probability?
We can never be certain of a diagnosis or its absence
What are the harms of seeking further certainty in tests?
time spent
money spent
radiation exposure
What is the basis of our decision on when to stop investigating?
based on the balance of the benefit from further information and the harm of further investigation
If the probability of disease is above the testing threshold?
- Further testing (questions, physical exams, labs..)is needed to move the probability past a threshold
- “test” zone
- differentials here are often called “active alternatives”
What are the factors to determine for setting testing threshold?
- Subjective
1. Severity of the condition- harms of ruling out a diagnosis that may be present
- Harms and accuracy of the available tests
- accuracy: how low is LR? how much info will it provide?
- harms: financial, time spent…
- consider the balance of accuracy of the test vs the harms of the test
- harms of ruling out a diagnosis that may be present
When to set low testing threshold?
- more severe condition
- more accurate available tests
- less harmful tests
If the probability of disease is below the testing threshold?
- stop doing tests
- “trash” zone
- differentials are considered “ruled out” or “excluded”
Should usually NOT set the testing threshold below the population prevalence (meaning anyone walking in is under testing zone).
True of False
True
When “test” zone expands? and “trash” zone shrinks
- greater harm of ruling out the condition if it is present
- more favorable balance of test harm relative to information benefit
When “trash” zone expands? and “test” zone shrinks
- less harm of ruling out the condition if it is present
- less favorable balance of test harm relative to information benefit
Can we take a differential out of the trash zone if symptoms change later?
Yes
