Critical Appraisal of Diagnostic Test Studies - Applicability

APPLICABILITY (or "generalizability" or "external validity") of diagnostic test studies are determined by considering whether this evidence would be useful for your patients:

• • is the test available now?

  • is it an acceptable test to the patient?

    • an invasive test is not that useful - it will carry risks that need to be weighed against the risk of the disease you're trying to diagnose

  • will I change my management based on the results of the test?

    • this is the classic question. Using likelihood ratios, if the likelihood of the disease doesn't change after you've applied the test, then there's really no reason to subject the patient to the test. I personally think it's wise to apply this question to ALL diagnostic tests you perform - what will I do differently with the results - you will be suprised about how many diagnostic tests you won't need.

Additional Resources:

• • QUADAS-2: A Revised Tool for the Quality Assessment of Diagnostic Accuracy Studies

  • CEBM - Toronto: Diagnostic Test Studies

  • CEBM - Toronto: Diagnostic Test Calculator

  • UIC: Diagnostic Test Calculator