Step 4: Apply the evidence to your patient

For any given pre-test probability, you can calculate a post-test probability.

Sources of information to determine the pre-test probabilities include: your or another colleague's clinical experience, statistics on frequencies of this disorder in the population, the frequency of the disorder in the study (from the 2x2 Table: (a+c/a+b+c+d = pre-test probability) or another study.

If you know the likelihood ratio positive and likelihood ratio negative, you can use our calculator to determine a post-test probability given any pre-test probability.

View calculators

Questions

Is the diagnostic test available, affordable, accurate, and precise in your setting?

Estimate your patient's pre-test probability (%)

How is your patient similar to the study population?

How is your patient different?

Will these differences affect the applicability of the test to your patient?

Determine your patient's post-test probability for a positive result (%). What will you do with a positive result?

Determine your patient's post-test probability for a negative result (%). What will you do with a negative result?

Will the results help your patient? Why or why not?