The 2008 World Health Report emphasizes the need for patient-centered primary care service delivery models in which patients are equal partners in the planning and management of their health. It is argued that this involvement will lead to improved management of disease, improved health outcomes and patient satisfaction, better informed decision-making, increased compliance with healthcare decisions, and better resource utilization. This article investigates the domains captured by the Effective Consumer Scale (EC-17) in relation to vulnerable population groups that experience health inequity. Particular focus is paid to the domain of health literacy as an area fundamental to patients' involvement in managing their condition and negotiating the healthcare system. In examining the possible influence of Outcome Measures in Rheumatology Clinical Trials (OMERACT) on health equity, we used the recent translation and validation of the EC-17 scale into Spanish and tested Argentina as an example. Future plans to use the EC-17 with vulnerable groups include formal collaboration and needs assessment with the community to tailor an intervention to meet its needs in a culturally relevant manner. Some systematic reviews have questioned whether interventions to improve effective consumer skills are appropriate in vulnerable populations. We propose that these populations may have the most to gain from such interventions since they might be expected to have relatively lower skills and health literacy than other groups.