How does the quality of care for type 2 diabetic patients benefit from GPs-nurses' teamwork? A staggered difference-in-differences design based on a French pilot program

In many countries, policies have explicitly encouraged primary care teams and inter-professional cooperation and skill mix, as a way to improve both productive efficiency gains and quality improvement. France faces barriers to developing team working as well as new and more advanced roles for health care professionals including nurses. We aim to estimate the impact of a national pilot experiment of teamwork between general practitioners (GPs) and advance practitioners nurses (APN)-who substitute and complement GPs-on yearly quality of care process indicators for type two diabetes patients (T2DP). Implemented by a not-for-profit meso-tier organisation and supported by the Ministry of Health, the pilot relied on the voluntary enrolment of newly GPs from 2012 to 2015; the staffing and training of APNs; skill mixing and new remuneration schemes. We use latent-response formulation models, control for endogeneity and selection bias by using controlled before-after and quasi-experimental design combining coarsened exact matching-prior to the treatment, at both GPs (435 treated vs 973 control) and T2DP levels -, with intention to treat (ITT; 18,310 in each group) and per protocol (PP, 2943 in each group) perspectives, as well as difference-in-differences estimates on balanced panel claims data from the National Health Insurance Fund linked to clinical data over the period 2010-2017. We show evidence of a positive and significant positive impact for T2DP followed-up by newly enrolled GPs in the pilot compared to the pretreatment period and the control group. The effect magnitudes were larger for PP than for ITT subsamples.