Beyond the gate: Referral style and utilisation of primary sector specialist care

While variation in general practitioners' (GPs') practice style is well documented, little is known about how these differences shape patients' use of specialist care beyond formal gatekeeping regulation. Using population-wide data from Denmark, we exploit residual variation in referral rates measured at the GP practice level to classify practices as restrictive, moderate, or liberal referrers and link these patterns to chronic care among individuals with type 2 diabetes. We find that patients listed with restrictive-referring practices are significantly less likely to adhere to foot and eye screening for diabetes-related complications. This pattern is observed both for referral-required specialised services (foot screening: -2.5 pp) and direct-access specialised services (eye screening: -2.6 pp), suggesting that GP practice behaviour is associated with differences in utilisation of specialist care across access pathways to a varying degree. Differences in screening uptake are concentrated among practices at the extremes of the referral distribution suggesting that only particularly restrictive referral behaviours stand out. Additional analyses reveal that direct-access specialist care is not associated with variation by patients' socioeconomic status. We also explore heterogeneity in uptake by patient characteristics and find consistent evidence of differential uptake across services. Lower socioeconomic status, living alone, non-Danish ethnicity and comorbidity are all independently associated with lower screening uptake pointing to systematic social inequities in access that cannot be explained by differences in clinical need. Our findings highlight that variation in GP practice style extends beyond referral-dependent services, and is associated with differences in patients' chronic care behaviour more broadly. We highlight the importance of addressing both patient-level barriers and variation in GP practice styles to improve screening uptake and equity in chronic disease management.