Diagnosis Worksheet

Diagnosis Worksheet Every clinician would like a diagnostic test that is 100% sensitive and 100% specific. However, in the real world this is never the case. Studies looking at a better diagnostic test must be carefully analyzed to avoid common pitfalls of population prevalence and pre-test probability.

Step 1: Why did they do this study? What question were they trying to answer?

Step 2: Define the Study Group

What were the inclusion criteria? What are the significance of these, if any?

What were the exclusion criteria? Was this appropriate?

Step 3: Making the Diagnosis Define the “reference test.” Is the comparison being made to the “Gold Standard?”

Were the study group subjected to both the “reference” test and the “standard” test? Was it blinded?

Step 4: Results What are the baseline characteristics of the study group? (usually Table 1.)

Are these similar to the patients you see?

Calculate Sensitivity, Specificity, Positive Predictive Value, Negative Predictive Value (use chart below)

Disease/Target Disorder Disease/Target Disorder Totals YES NO Test Positive A B A+B

Test Negative C D C+D Totals A+C B+D What is the sensitivity of the test? a/(a+c)

What is the specificity of the test? d/(b+d)

How does this compare to the comparison test?

What is the Positive Predictive Value? a/(a+b)

What is the Negative Predictive Value? d/(c+d)

Calculate Likelihood Ratio (+) LR+ = sensitivity/ (1-specificity)

Calculate Likelihood Ratio (-) LR(-) = (1-sensitivity)/specificity Step 6: Discussion Points/Questions

What are the advantages and disadvantages of this test compared to the Gold Standard?

Is the prevalence of the disease in our population similar to the study population?

Does this study look at pre-test probability? How does it compare to our population?

Is the test available to our patients? Is it affordable?

Was this test independently validated in another group of patients?

Most importantly, do you think this changes the morbidity or mortality of the disease we are trying to detect?

For further study, for those interested in research…

During the initial reading, imagine you are the researchers doing the study and see if you would approach it the same way. Then, after reviewing the article, do an after-action-review and see if you would do anything different knowing the results.