Nationwide Utilization of Danish Government Electronic Letter System for Increasing Guideline-directed Medical Therapy in Chronic Kidney Disease

The study is a prospective, 2x2 factorial, registry-based, randomized, open-label implementation trial. The study population will consist of Danish adults diagnosed with CKD. Participants will be identified through Danish nationwide health registries using codes from the International Classification of Diseases, 10th revision (ICD-10).

The primary objective of this study is to investigate the effects of electronically sent nudging letters delivered directly to (1) patients with CKD and, separately, (2) electronically sent nudge letters delivered to GPs of the included CKD patients on the primary outcome of use of GDMT defined as at least one prescription of RASi or SGLT2i 6 months after intervention delivery in patients with CKD.

Patients with CKD will be randomized (1:1) to either a control arm (no digital nudge letters sent to the patient) or an intervention arm (a digital nudge letter). GPs of the enrolled patients with CKD will be randomized (1:1) to a control arm (no digital nudge letters sent to the GP) or an intervention arm (a digital nudge letter). The letters will inform the recipients about the importance of GDMT in CKD and that updated Danish guidelines for treating CKD are available. The letter to the GPs will also include the definition of CKD and a summary of the guidelines.

The interventions will be delivered through the official, mandatory Danish electronic letter system. All subject data will be retrieved from the Danish nationwide registries except for information on intervention allocation. Endpoints will be retrieved at prespecified dates using prespecified search algorithms.

This study will coincide with the release of the updated clinical guidelines on the treatment of CKD by the Danish Society of Nephrology.

Inclusion criteria

• Age +18 years
• Diagnosis of CKD defined as at least one hospital encounter with the following ICD-10 codes in the primary diagnostic positions within ≤ 5 years: N18- N19, I12, E102, E112, E132, E142.

Exclusion criteria

For patient-level intervention comparisons:

• Exemption from the official, mandatory Danish electronic mailbox system.

For general practice-level intervention comparisons:

• Individuals on a patient list of general practice clinics run by Danish administrative Regions.
• Individuals not on a patient list of a general practice.