Evidence for Diagnostic Tests

There are 6 levels of diagnostic test quality that we should consider: (Fryback 1991)

  1. Technical quality of the test information
  2. Diagnostic accuracy
  3. Change in the physician’s diagnostic thinking
  4. Change in management plans
  5. Change in patient outcomes
  6. Societal costs and benefits

We frequently assume that if a test has great diagnostic accuracy that it should be used in practice, but a glance at this list reminds us that it is really patient outcomes that we should care about. Tests with increased sensitivity may appear better, but in fact might be detecting a new spectrum of disease. Therefore, one cannot simply extrapolate improved detection with better patient outcomes. (Lord 2006)


Fryback DG, Thornbury JR. The efficacy of diagnostic imaging. Medical decision making : an international journal of the Society for Medical Decision Making. ; 11(2):88-94. PMID: 1907710

Lord SJ, Irwig L, Simes RJ. When is measuring sensitivity and specificity sufficient to evaluate a diagnostic test, and when do we need randomized trials? Annals of internal medicine. 2006; 144(11):850-5. PMID: 16754927

Cite this article as:
Morgenstern, J. Evidence for Diagnostic Tests, First10EM, January 7, 2018. Available at:

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