Substitution or addition: An observational study of a new primary care initiative in the Netherlands.

In 2014, the Primary Care Plus (PC+) model was introduced in the Netherlands to shift low-complex specialised care from the hospital to the primary care setting. While positive effects of PC+ have been documented at individual patient level concerning health-related quality of life, perceived quality of care and care costs, its impacts on service use at the population level remain uncertain. In this observational study, we used retrospective health insurance reimbursement claims data from the largest health insurer in the intervention region to determine service use. We assessed PC+ and secondary care insurance claims (i.e. claims of the regional hospital and claims of other secondary care settings in and outside the region visited by patients from the intervention region) from 2015 to 2018 and compared these to the national level. The total number of claims related to low-complex specialised care in the intervention region showed an increase over time. The increase in claims was related to PC+. The number of claims related to the regional hospital and other secondary care settings decreased over time. During the same period, a declining trend in claims at the national level was observed. The introduction of the PC+ model in one region in the Netherlands was associated with an increase in the use of low-complex specialised care. This suggests that the ability of the PC+ model to substitute for specialist care at population level may be limited. Going forward, it will be important to continue monitoring and evaluating service use as substitution effects may materialise only over a longer timeframe.