MUSM Libraries: Evaluating a DIFFERENTIAL DIAGNOSIS article

Validity issues  | For a specific patient |  Finding articles

Validity issues

Are the results valid?

  1. Did the investigators enroll the right patients? Was the patient sample representative of those with the clinical problem?
  2. Was the definitive diagnostic standard appropriate? Was the diagnostic process credible?
  3. For initially undiagnosed patients, was follow-up sufficiently long and complete?

What are the results?

  1. What were the diagnoses and their probabilities?
  2. How precise are these estimates of disease probability?

Will the results help me in caring for my patients?

  1. Are the study patients similar to my own?
  2. Is it unlikely that the disease possibilities or probabilities have changed since this evidence was gathered?

For a specific patient

Diagnostic Hypothesis Description Implications for Testing
1. Leading hypothesis or "working diagnosis" Single best explanation of patient's illness Choose test to confirm:
high specificity
High LR + (greater than 1)
2. Active alternatives or "rule outs" Not as good as #1, but likely serious or treatable enough to be actively sought in this patient. Choose tests to exclude:
High sensitivity
Low LR - (less than 1)
3. Other alternatives Not likely, serious or treatable enough to be pursued now, but not yet excluded. Hold off on tests now
(may test for these later)
4. Excluded hypotheses Causes of the problem that have been disproved. No further test necessary.

Finding articles about differential diagnosis

PubMed:
PubMed for Handhelds (Memorial On-Campus/Remote One and Mercer On-Campus access)
PubMed for Handhelds (Mercer Off-Campus access)

References:

From: Sackett, D.L. Evidence-Based Medicine. How to Practice and Teach EBM. Churchill-Livingstone, 3rd edition, 2005 (pocket cards).

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