Health Services Research
Users' Guides to the Medical Literature
Evidence-Based Medicine Working Group

Three Initial Questions
Were the outcome measures accurate and comprehensive?
Were there clearly identified, sensible comparison groups?
How well did the compared groups match up on important factors that can affect the outcomes of a health service:

a. Who provided the service?
b. What service was provided?
c. When was the service provided?
d. Where was the service provided?
e. How was the service provided?

Further Questions
Were all important prognostic factors measured?
Were measures of patients' prognostic factors reproducible and accurate?
Were patients similar with respect to these factors?
How much difference in outcome(s) remains after adjustment for the prognostic factors?

JAMA, 1996; 275: 554-558