Methodological reflections on identifying and reaching groups left behind from health programs for fieldwork in Kerala, India.

A plethora of tools have been used to understand health inequities. While these could be well-executed in a controlled environment, the uncertainties of working in a community lead to challenges that are sometimes beyond researchers' control. This is further aggravated while working with 'vulnerable' population sub-groups. As part of a larger health systems research project focused on health inequalities, we sought to identify these groups to assess their needs. We discussed in this article, our methodological reflections on trying to identify and carry out research with groups left behind, and the way we approached the challenges incurred during the data collection process. Identifying 'vulnerable' groups required constant interrogation and questioning of the very definition of 'vulnerability' in varied contexts and in relation to other groups facing disadvantages. Different strategies were used, including snowball sampling from FGD participants. Even when identified, we found that in some cases, the FGD method was inappropriate for fieldwork and that the ethical requirement of ensuring some care access for study participants became increasingly difficult to assure. Equity-oriented research must involve constant reflexivity around such ethical dilemmas, which we feel are too often ignored -just as some 'vulnerable' populations are- in typical (writing about) research studies. Supplementary Information: The online version contains supplementary material available at 10.1186/s12982-025-01016-4.