TABLE 1

Critical Appraisal Questions Used by the USPSTF in Evaluating Evidence

1. Do the studies have the appropriate research design to answer the key question(s)?
2. To what extent are the existing studies of high quality? (ie, What is the internal validity?)
3. To what extent are the results of the studies generalizable to the general US primary care population and situation? (ie, What is the external validity?)
4. How many studies have been conducted that address the key question(s)? How large are the studies? (ie, What is the precision of the evidence?)
5. How consistent are the results of the studies?
6. Are there additional factors that assist us in drawing conclusions (eg, presence or absence of dose-response effects, fit within a biologic model)?