The population-level costs of immunosuppression medications for the treatment of glomerulonephritis are increasing over time due to changing patterns of practice.

Abstract

Immunosuppression (IS) is the main treatment for most types of glomerulonephritis (GN). Quantifying the cost of IS is necessary to ensure equitable access to therapies and optimal health outcomes, but the real-world cost of IS treatment for GN is largely unknown. We examined temporal changes in the population-level IS medication costs for GN over a 14-year period in a large Canadian province. We linked a provincial pathology database (containing all GN cases from 2000 to 2012) with renal and medication administrative databases to capture clinical characteristics and IS medications, with follow-up until 2013. The primary outcome (mean IS medication cost per treated patient each year) was evaluated for trends over time. The cohort included 2983 GN patients followed for a mean of 5.7 years. The yearly per-patient medication cost increased 6.8-fold from $205 to $1394 (P < 0.001), with significant increases of 3.5-11.7-fold in anti-neutrophil cytoplasmic antibody (ANCA) vasculitis, focal segmental glomerulosclerosis, lupus nephritis, minimal change disease and membranous nephropathy (P ≤ 0.004), but no change in immunoglobulin A (IgA) nephropathy. The cost of mycophenolate mofetil, calcineurin inhibitors and rituximab increased significantly (P < 0.001) such that in 2000 they accounted for 17.6% of medication costs and were used by 2.2% of patients, which increased to 94.5% and 44.6%, respectively, in 2013. The costs of azathioprine, cyclophosphamide and prednisone increased only slightly or decreased. Patterns of drug use and contribution to cost varied by type of GN. These are the first population-level estimates of the IS treatment costs for GN, and demonstrate a striking increase due to changing practice patterns from older, cheaper medications to newer, more expensive therapies. These results provide important information to guide future health policy strategies and cost-effectiveness research in glomerular diseases.