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Evidence-Based Practice: Diagnosis

Critical Appraisal of Diagnosis Articles

1. Are the results of the diagnostic study valid?
  • Was there an independent, blind comparison with a gold standard of diagnosis?
  • Was the diagnostic test evaluated in an appropriate spectrum of patients?
  • Was the gold standard applied regardless of the diagnostic test result?
  • Was the test validated in a second, independent group of patients?
2. What are the results?
  • Does this diagnostic test accurately distinguish between patients who do and do not have a specific disorder? 
    • Sensitivity: Proportion of people with disease who have a positive test result.
    • Specificity: Proportion of people without disease who have a negative test result.
    • Likelihood Ratios: The likelihood that a given test result would be expected in a patient with the target disorder compared with the likelihood that this same result would be expected in a patient without the target disorder.
3. Are the results relevant to your patient?
  • Will the reproducibility of the test result and its interpretation be satisfactory in your clinical setting?
  • Are the study results applicable to the patients in your practice?
    • Are the study patients similiar to your own?
    • Do the test properties change, yield different likelihood ratios, due to disease severity or a different distribution of competing conditions?
  • Will the test results change your managment of the patient?
    • What are the test and treatment thresholds for this disease? Does the diagnostic test meet the treatment threshold?
  • Will your patient be better off as a result of the test?
    • Is the target disease, if left untreated, dangerous?
    • Do the benefits of the test outweigh its risks?
    • Does effective treatment exist?
    • Does the test yield useful information, otherwise unavailable, that leads to a change in management of your patient that is beneficial?

Diagnosis Critical Appraisal Worksheet

Diagnostic Statistics Calculators


Critical appraisal questions come from the following sources:
Guyatt, G. Rennie, D. Meade, MO, Cook, DJ.  Users’ Guide to Medical Literature: A Manual for Evidence-Based Clinical Practice, 2nd Edition 2008.
Sackett, DL, et al. Evidence Based Medicine: How to Practice and Teach EBM. 2nd ed. Edinburgh: Churchill Livingstone, 2000. BHSL Call Number: WB 102 E933 2000
Tips on Critical Appraisal of Evidence: DiagnosisCentre for Evidence Based Medicine (Toronto)
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