Socially disadvantaged persons, such as the homeless and the non-insured, have a worse physical and mental health status than comparable populations. Social institutions make a significant contribution to the medical treatment and social worker support of these persons. This research report addressed the question of relevant evaluation methods, indicators and instruments for the evaluation of easily accessible, outpatient health centres for vulnerable groups.

We conducted a systematic literature search in several databases and a hand search on the websites of specialist societies for evaluations. Furthermore, several experts in the field were contacted.

In total, we identified twelve evaluation studies (in English) and seven evaluation reports (in German). The selected publications reported on evaluation methods, indicators and/or instruments focusing on low-threshold outpatient health care facilities. There was a high degree of methodological heterogeneity according to the thematic backgrounds and objectives – however, the majority of the publications involved a 'mixed methods' approach. These were mainly interviews and questionnaires. With regard to the evaluation indicators used, socio-demographic data, patients’ health status as well as the use of health and social services were collected primarily. Only a few publications reported on health economic indicators. There were also few studies that provided information on evaluation instruments. The mental health status of the patients was measured most frequently. In this respect, both generic and disease-specific instruments were reported.

The concluding recommendations for the planning and implementation of such an evaluation include, for example, the consideration of participatory evaluation approaches to involve these "hardly to reach populations" in the design and conduct of the evaluation, as well as the development of a logic model as a basis for identifying adequate evaluation methods, indicators and instruments.