Fig. 2

The conceptual Population-Intervention-Environment-Transfer Model of Transferability (PIET-T) focuses on the perspective of the decision-maker, who seeks to improve the health situation of the target population (or person) and aims to transfer an intervention from a primary context to the target context. It is assumed that the population (P), the intervention (I), and the environment (E) in the primary and the target context influence one another. The combination of these three constructs determines the resulting outcome. The decision-maker collects information on the evidence established in a primary context. The primary context symbolizes the form in which evidence was gained and is available. In order to decide on the transfer of the intervention, the decision-maker needs to take into account the conditions of the primary context and his or her own context. The transfer can take place on different levels in the target context, for example, the national level, the local or community level, the organizational level, or the individual level. Therefore, the research design and the three constructs of the primary context should be compared with the level of transfer and the three constructs in the target context. Considering transferability, an adaptation of the intervention to the target context may be necessary. The information gained from the primary context influences how the transfer is designed. At the same time, designing and realizing the transfer requires the consideration of the constructs of the target context, since transferability also depends on the interaction of these three constructs. Therefore, the population, the intervention, and the environment in the primary and target context as well as the transfer itself influence transferability of health interventions