Testing Thresholds

Question 1

Differentials in the “trash” zone are considered

Answer 1

ruled out or excluded

Question 2

if the probability of disease is below the testing thresholds:

Answer 2

• stop doing tests related to that specific differential diagnosis

Question 3

Factors to consider when establishing a threshold:

Answer 3

1. the condition: harms of ruling out a diagnosis that may be present
2. The test: how harmful is the test and how much information will it provide?
   Harms include: financial, time and other

Consider the patient values and preferences

Question 4

Should not set the testing threshold below the population ___________.

Answer 4

population prevalence

This would suggest that you think someone take at random from the population is in the testing zone, implying at least that you think everyone who walks into your office should be investigated for the condition

Question 5

ASK yourself: “Would I be comfortable sending the patient
home with an x% chance that they had this condition when
[some test] is available?”

Question 6

The test zone expands (and “trash” zone shrinks) if:

Answer 6

• greater harm of ruling out the condition if it is present
• more favourable balance of test harm relative to information benefit

Question 7

The “trash” zone expands (and test zone shrinks) if:

Answer 7

• less harm of ruling out the condition if it is present
• less favourable balance of test harm relative to information benefit

Question 8

________ thresholds set a probability below which we stop
diagnostic work-up. We do this because complete certainty is
impossible

Answer 8

testing thresholds

Question 9

Testing thresholds are set according to the harm of
inappropriately ruling _____ a diagnosis and the ______ of the
harms and benefits of testing

Answer 9

ruling out

the balance of the harms and benefits of testing

Question 10

When the probability of disease is above a testing threshold,
___________ is needed. When it is
below a testing threshold, we _____ the diagnostic work-up for that
condition.

Answer 10

further testing or other management is needed. when below, we stop