Patients with idiopathic membranous nephropathy: A real-world clinical and economic analysis of U.S. claims data

Abstract

BACKGROUND: Membranous nephropathy (MN) is a common cause of nephrotic syndrome in nondiabetic adults. Approximately one third of patients with MN progress to end-stage renal disease (ESRD), while others may be successfully treated to remission. Patients with MN represent a high-risk population for whom management strategies can alter and improve outcomes. Currently, there is little real-world evidence regarding the burden of MN on health plans. OBJECTIVES: To (a) characterize clinical and economic outcomes during a 1-year time frame among a prevalent cohort of patients with MN and (b) compare the 5% of patients incurring the highest cost with the remaining 95%. METHODS: A retrospective analysis of commercially insured patients was conducted using MarketScan administrative health care claims data from January 1, 2012, to December 31, 2015. Patients were aged ≥18 years, enrolled in a fee-for-service plan, and had ≥2 medical claims for an MN diagnosis (ICD-9-CM codes 581.1, 582.1, and 583.1). Diagnoses indicating clear secondary causes were excluded wherever possible. Demographics were determined as of the first diagnosis date; clinical characteristics (e.g., MN-specific therapy, complications, and procedures), health care resource utilization (HCRU; inpatient, outpatient including other outpatient and emergency department [ED], and prescriptions), and costs were evaluated for 1 year following MN diagnosis. Total costs and cost distribution (2017 U.S. dollars) were examined using plan-paid and patient-paid amounts. The 95th percentile was used to categorize and compare the subcohorts: high-cost cohort (HCC) patients (top 5%) and non-high-cost cohort (NHCC) patients (the remaining 95%). Descriptive analyses, chi-square tests, and Wilcoxon rank-sum tests were conducted. RESULTS: 2,689 patients were identified (60.0% male, mean age=46.4 years). Severity and advanced disease were observed in a higher proportion of HCC patients (n=134) versus NHC patients (n=2,555) via adverse health outcomes, procedures, and immunosuppressant use. HCC patients used significantly more resources on average than NHCC patients (additional use): 1.7 inpatient, 1.2 ED, and 4.8 outpatient office visits; 15 prescriptions; and 64.8 other outpatient visits (i.e., outpatient, hospital, and ESRD facilities). Total MN-related cost and mean (SD) cost per patient were $123.2 million and $45,814 ($101,353); HCC patients accounted for 43.7% of total costs for a mean cost per patient of $401,608 versus NHCC patients at 56.3% and mean cost per patient of $27,154. The greatest costs for both groups were related to outpatient visits (HCC=46.7%; NHCC=52.8%), inpatient visits (HCC=27.7%; NHCC=28.6%), and prescriptions (HCC=25.7%; NHCC=18.6%). CONCLUSIONS: Patients with MN are significantly burdened with high disease severity and adverse health outcomes, resulting in substantial HCRU and costs. Health plan cost drivers for MN (HCC and NHCC patients) occurred primarily in the outpatient setting, followed by the inpatient setting and prescriptions. Modifiable aspects preceding progression to advanced renal disease and worse outcomes should be explored to identify effective interventions and improve resource allocation earlier in the disease pathway, before ESRD.