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

<h2>Abstract</h2><h3>Rationale & Objective</h3> 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 (HCRU)/costs for IgAN patients with high-risk proteinuria and worsening kidney function in Europe. <h3>Study Design</h3> Retrospective, descriptive analysis of anonymized TriNetX data (2015–2023). <h3>Setting & Participants</h3> Individuals from the UK, Spain, and Germany with an IgAN diagnosis recorded between 2015–2022. <h3>Predictors</h3> Proteinuria and CKD stage. <h3>Outcomes</h3> Cost per visit (inpatient, outpatient, emergency visits), total cost, and mean costs per patient. <h3>Analytical Approach</h3> HCRU 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 due to insufficient data available. <h3>Results</h3> In both Spain and the UK, the average number of inpatient (Spain 1.9‒2.5; UK 2.2‒11.0) and outpatient (Spain 13.2‒38.9; UK 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 were low (2.9‒4.3). The average annual composite cost per patient for all visit types were greater in patients with higher CKD stage and proteinuria levels in Spain (CKD stage G1‒G2, <0.5 g/day: €487.00 vs CKD stage G5, ≥2 g/day: €26,559.44), and the UK (CKD stage G1‒G2, <0.5 g/day: £432.95 vs CKD stage G5, ≥2 g/day: £36,253.80). <h3>Limitations</h3> Electronic medical records may be subject to misclassification, incorrect coding, and documentation errors. <h3>Conclusions</h3> This study highlights the association between declining kidney function, increased proteinuria, and considerable economic burden.