Background: The acute geriatric community hospital (AGCH) is an alternative to conventional hospitalisation of older adults. At the AGCH, patients receive acute medical specialist treatment in combination with early rehabilitation in an fitting environment by an interdisciplinary team of professionals. Ambiguity exists on the exact definition of the target group for the AGCH and the difference with the target groups for bed-based intermediate care and geriatric hospital care models.
 Objective: Limited guidelines and methods exist to refine the target group of new care model or (complex) health interventions. The aim of this study was to provide refined assessment criteria for the AGCH by using a target-group refinement procedure with case vignettes.
 Design: A design based research using qualitative research techniques. 
 Setting: Two pioneer sites who have an AGCH in their region and seven pioneer sites who have the ambition to implement an AGCH in their region.
 Subjects: A total of 20 healthcare professionals (elderly care physicians, clinical geriatricians and other medical specialists, physician assistants, nurse specialists) participated in the AGCH target group refinement project, either active in hospitals (n=10) or intermediate care facilities (n=7) or skilled nursing facilities (n=3), and all involved in the implementation of an AGCH in their region.
 Methods: The developed target-group refinement procedure consisted of three phases. 1) Healthcare professionals from the pioneer sites were asked to submit case vignettes for a specific care type or an ambiguous boundary between the AGCH and other care models. These case vignettes were reviewed during 2) web-based vignette questionnaires and 3) two online working sessions. Both during phase 2 and 3, participants were asked to make a referral decision for the case vignettes they were presented with and to report their considerations during this process.
 
 Results: In total, 23 case vignettes were collected and reviewed by 18 healthcare professionals. Triage dilemmas were identified and discussed during online working sessions, following from which the AGCH assessment criteria were refined. We found that the final referral outcome is the result of an interplay of clinical and organisational triage factors.
 Conclusions: This target group refinement procedure enabled involving of a variety of healthcare professionals and was suitable to refine the AGCH assessment criteria. In a short time period, it provided us further insight into (1) the required changes to the AGCH assessment criteria; (2) the (ambiguous) boundaries between the AGCH and other care models, and (3) the considerations made by healthcare professionals during referral decision-making for older adults with an acute care need. We recommend to use this novel procedure as a tool for specifying the target group of (new) care models or healthcare interventions.