How much variation in the nonsurgical interventions is acceptable? Can different study sites use different approaches within the same treatment arm? How should applicants approach the issues of fidelity and intensity?

Any intervention(s) proposed for comparison should be described and justified as to the extent of variation that will be allowed across different sites in consideration of potential impacts upon the study’s representativeness, feasibility, and internal validity.  

As noted in the PFA, “…applicants should refer to the multiple elements of the pragmatic-explanatory continuum and explicitly consider the tradeoffs of each element on the continuum. Absolute pragmatism is not the ideal, particularly for the standardization of interventions chosen for comparison. Interventions require some degree of flexibility in their use but must be sufficiently well-defined to be replicable in their dissemination and implementation in U.S. health care.”