Clinical Characteristics as Predictors of Healthcare Resource Utilization in Immunoglobulin A Nephropathy: A Retrospective Database Study.

Background: Progression rates in immunoglobulin A nephropathy (IgAN) are variable, making future healthcare needs in this patient population difficult to anticipate. Objectives: We sought to determine whether baseline patient characteristics at biopsy diagnosis are predictive of subsequent healthcare resource utilization (HCRU) in individuals affected by IgAN. Methods: This was a longitudinal, retrospective cohort study of members enrolled in Kaiser Permanente Southern California, a racially, ethnically, and socioeconomically diverse population. We extracted data on members diagnosed with primary IgAN based on kidney biopsies performed from 2000 to 2021. Statistical associations between indicators of disease severity at baseline and subsequent HCRU were evaluated. The baseline variables assessed were chronic kidney disease (CKD) stage, urine protein creatinine ratio (UPCR), and the individual burden of comorbidities expressed as Elixhauser Comorbidity Index. The HCRU outcomes were emergency department visits, inpatient visits, outpatient visits, radiology, laboratory, and medication dispensations within 2 years after biopsy, all expressed as utilization per patient per month (PPPM). Results: A total of 612 adults with primary IgAN were identified. Worse baseline CKD stage and UPCR exhibited statistically significant positive correlations with the PPPM for aggregate HCRU. Patients in CKD stage G4 had an overall PPPM of 2.94, which was significantly (P < .01) greater than for each milder CKD category (1.56-2.04). Patients with UPCR >2 g/g had an overall PPPM (2.38), which was significantly (P < .01) greater than each milder UPCR category (1.70-1.84). Aggregate PPPM showed a numerically increasing trend from the least (<0.5 g/g) to most severe UPCR category (>2 g/g). CKD stage, UPCR, and comorbidity score all correlated significantly with individual HCRU outcomes. Discussion: Easily assessed patient baseline variables including CKD stage, proteinuria, and comorbidities are predictive of HCRU in primary IgAN. Our findings are consistent with recent IgAN management guidelines designating proteinuria ≥0.5 g/g as indicative of elevated progression risk. Conclusions: Patient clinical characteristics can be used to estimate future HCRU in IgAN, facilitating cost-benefit analysis. The accurate estimation of anticipated HCRU is becoming increasingly important in IgAN as new, disease-specific therapies become available for this long-term, progressive condition.