Health Care Resource Utilization and Associated Costs Across Proteinuria and Declining Kidney Function in Patients With IgA Nephropathy: A Retrospective Study in Three European Countries

Rationale & Objective: Immunoglobulin A nephropathy (IgAN) is the leading cause of chronic kidney disease (CKD) and end-stage kidney disease. Few studies have assessed health care resource utilization and costs for IgAN patients with high-risk proteinuria and worsening kidney function in Europe. Study Design: Retrospective, descriptive analysis of anonymized TriNetX data (2015-2023). Setting & Participants: Individuals from the United Kingdom, Spain, and Germany with an IgAN diagnosis recorded between 2015 and 2022. Predictors: Proteinuria and CKD stage. Outcomes: Cost per visit (inpatient, outpatient, emergency visits), total cost, and mean costs per patient. Analytical Approach: Health care resource utilization and costs were analyzed within a year post-index date and stratified by visit type, CKD stage, and proteinuria levels, with costs obtained from official and published sources. UK/Spain costs were also stratified by a composite variable considering both CKD and proteinuria levels. This was not done for Germany because available data was insufficient. Results: In both Spain and the United Kingdom, the average number of inpatient (Spain, 1.9-2.5; United Kingdom, 2.2-11.0) and outpatient (Spain, 13.2-38.9; United Kingdom, 5.3-13.9) visits per patient increased with increasing CKD stages 1-5; this trend was not noted for emergency visits. In comparison, the number of outpatient visits per patient with CKD stages 1-5 in the German cohort was low (2.9-4.3). The average annual composite cost per patient for all visit types was greater for patients with higher CKD stage and proteinuria levels in Spain (CKD stage G1-G2, <0.5 g/d: €487.00 vs CKD stage G5, ≥2 g/d: €26,559.44) and the United Kingdom (CKD stage G1-G2, <0.5 g/d: £432.95 vs CKD stage G5, ≥2 g/d: £36,253.80). Limitations: Electronic medical records may be subject to misclassification, incorrect coding, and documentation errors. Conclusions: This study highlights the association between declining kidney function, increased proteinuria, and considerable economic burden.