Treatment Thresholds

Question 1

T or F: We can never be certain of a diagnosis or its absence (i.e. we
can’t reach 100% or 0% probability)

Answer 1

TRUE

Question 2

If the probability of disease is below the treatment threshold:

Answer 2

1. further testing (questions, physical exams, labs, etc.) is needed to move the probability past a threshold

Question 3

Differentials in the test zone are also called:

Answer 3

active alternatives

Question 4

if the probability of disease is above the treatment threshold:

Answer 4

consider treatment with that particular treatment
“treatment” in a broad sense: could be referral, education, supplement etc.

Question 5

A diagnosis in the treatment zone is often called the

Answer 5

“working diagnosis”

Question 6

How do you determine a threshold?

Answer 6

• consider the condition and the harms of leaving the condition untreated
• consider the test, its accuracy, the harms of testing, the cost, time spent, others. Considers the patient’s values and preferences
• consider the treatment. the benefits of treatment, the cost, time spent, and side effects. Consider the patient’s values and preferences

Question 7

The test zone expands (and the treatment zone shrinks) if:

Answer 7

1. lower harms of leaving the condition untreated
2. more favourable balance of test harm relative to information benefit
3. less favourable balance of treatment harm relative to benefit

Question 8

The treatment zone expands (and the test zone shrinks) if:

Answer 8

1. higher harms of leaving the condition untreated
2. less favourable balance of test harm to information benefit
3. more favourable balance of treatment harm to benefit

Question 9

Lowered (increasing testing area and decreasing “trash” area) by:

Answer 9

• Greater harm of ruling out the
  condition if it is present
• More favorable balance of test
  harm relative to information benefit

Question 10

Most strokes are ischemic (something blocks a blood vessel in
the brain)

• These are treated with a thrombolytic (“clot-busting”) drug
• However, administering this drug in a case of a hemorrhagic
  stroke can make it worse

Where would the treatment threshold be?

Answer 10

Treatment threshold for thrombolytic drug is high

Question 11

Temporal arteritis is a rare condition that occurs in older
individuals and can lead to blindness if not treated quickly with
corticosteroids

Treatment is recommended before confirmatory biopsy is
performed; corticosteroids can be stopped if biopsy is negative

Where would treatment threshold be?

Answer 11

Treatment threshold for initiating corticosteroids is very close to the testing threshold (LOW)