Maintaining Internal Validity in Community Partnered Participatory Research: Experience from the Community Partners in Care Study.

Objective: With internal validity being a central goal of designed experiments, we seek to elucidate how community partnered participatory research (CPPR) impacts the internal validity of public health comparative-effectiveness research. Methods: Community Partners in Care (CPIC), a study comparing a community-coalition intervention to direct technical assistance for disseminating depression care to vulnerable populations, is used to illustrate design choices developed with attention to core CPPR principles. The study-design process is reviewed retrospectively and evaluated based on the resulting covariate balance across intervention arms and on broader peer-review assessments. Contributions of the CPIC Council and the study's design committee are highlighted. Results: CPPR principles contributed to building consensus around the use of randomization, creating a sampling frame, specifying geographic boundaries delimiting the scope of the investigation, grouping similar programs into pairs or other small blocks of units, collaboratively choosing random-number-generator seeds to determine randomized intervention assignments, and addressing logistical constraints in field operations. Study protocols yielded samples that were well-balanced on background characteristics across intervention arms. CPIC has been recognized for scientific merit, has drawn attention from policymakers, and has fueled ongoing research collaborations. Conclusions: Creative and collaborative fulfillment of CPPR principles reinforced the internal validity of CPIC, strengthening the study's scientific rigor by engaging complementary areas of knowledge and expertise among members of the investigative team.