Treatment thresholds

Question 1

Clinical utility:

Answer 1

-We can never be certain of a diagnosis or its absence
ex) we cant reach 100% or 0% probability

-Every test has a cost: seeking further certainty incurs further harm
ex) time spent, money spent, radiation exposure

-Every treatment has harms and benefits

-We must therefore decide (ideally in advance) when to stop investigating based on the balance of the benefit from further information and the harm of further investigation as well as the balance of the harms and benefits of treatment

Question 2

Testing threshold “zones”:

If the probability of disease is below the treatment threshold:

Answer 2

-Further testing (questions, physical exams, labs etc.) is needed to move the probability past threshold

-“test” zone

-Differentials in this zone are often called “active alternatives”

Question 3

Testing threshold “zones”:

If the probability of disease is above the treatment threshold:

Answer 3

-Consider treatment with that particular treatment

-“treatment” in a broad sense: could be referral, education,

-“treat” zone

-Diagnosis here is often called the “working diagnosis”

Question 4

Where is your threshold?

Answer 4

Subjective:

Factors:

The condition: harms of leaving the condition untreated.

The test:
-Accuracy: How high is the LR, ex) how much information would it provide?

-Harms of testing: financial, time spent, other

note: there are many potential harms; consider patient values and preferences.

The treatment:
-Benefits of treatment
-Harms of treatment: financial, time spent, side effects, etc.

Note: there are many potential harms; consider patient values and preferences

Question 5

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

Answer 5

-Lower harms of leaving the condition untreated

-More favorable balance of test harm relative to information benefit

-Less favorable balance of treatment harm relative to benefit

Question 6

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

Answer 6

-Higher harms of leaving the condition untreated

-Less favorable balance of test harm to information benefit

-More favorable balance of treatment harm to benefit

Question 7

Testing vs. Treatment thresholds:

Answer 7

cont’d:

Question 8

Summary:

Answer 8

1) treatment thresholds set a probability above-which which we consider treatment. We do this because complete certainty is impossible.

2) Treatment thresholds are set according to the harm of leaving a condition untreated, the balance of the harms and benefits of testing, and the balance of harms and benefits of the treatment

3) When the probability of a condition is below a treatment threshold, further testing is needed. When it is above a treatment threshold, we consider that particular management option for the condition in question.