[2] Diagnostic Research Design Flashcards
(34 cards)
Do you need a diagnosis if pretest probability is 100%?
No, it is not needed
Define: Treatment Threshold
Probability above which diagnosis is sufficiently likely to warrant treatment
What is the effect of a greater adverse effect of treatment on the Treatment Threshold?
Higher Threshold
What is the effect if the next test the patient has to be subjected to is more invasive than the current test to be performed on the Treatment Threshold?
Lowered Threshold
Prevents more people from being subjected to the next more invasive test
Define: Test/Diagnostic Threshhold
Probability below which a diagnosis warrants no further consideration
What is the effect of a serious missed diagnosis on the Test/Diagnostic Threshold?
Lowered Threshold
Missing diagnosis would be fatal, lowering it would ensure more people to take further tests to confirm
What is the effect if the next test to be done is riskier than the current test on the Test/Diagnostic Threshold?
Higher Threshold
This is done to ensure less people take the riskier next test if they don’t reach the high enough diagnosis warrant in the first place
[Formula]
Likelihood Ratio
Probability of Person w/ the Disease Testing Positive / Probability of a Person w/o the Disease Testing Negative
[Interpretation]
LR > 1
Increased disease probability
[Interpretation]
LR < 1
Decreased disease probability
[T/F]
Diagnostic tests with LRs close to 1 have practical significance
F
Goal is create a significant increase in the post test probability as compared to pre test probability
[Interpretation]
LRs > 10 and < 0.1
Large and often conclusive
[Interpretation]
LRs 5-10 and 0.1-0.2
Moderate Shifts
[Interpretation]
LRs 1-2 and 0.5-1
Small and Rarely Important
[Interpretation]
LRs 5-10 and 0.2-0.5
Small but Sometimes Important
Definition: Gold Standard
Accepted definition of disease and can dictate presence or absence of it
[Gold Standard]
Pulmonary TB
Chest X-Ray Histopathology Autopsy Anti-Kochs Sputum Culture
[Gold Standard]
Pneumonia
Chest X-Ray
Histopathology
Sputum Culture
[Gold Standard]
Systemic Lupus Erythematosus
Expert’s Opinion
[Gold Standard]
Embolic CVD
CT Scan + 2D Echo
Need Both
Definition: Sensitivity
Probability of a positive test among diseased
Sensitive tests are more important for generalists or specialists?
Why?
Generalists
To not miss people with the disease
Definition: Specificity
Probability of a test being negative among non-diseased people
A positive test is more helpful for Specific or Sensitive tests?
Specific Tests
