Introduction:
Immunoglobulin A nephropathy (IgAN) is a leading cause of glomerulopathy worldwide, with overall global incidence of 2.5 per 100,000 people per year. As of 2023, the annual incidence and point prevalence of IgAN are estimated to be 0.76 per 100,000 and 2.53 per 10,000 in Europe, respectively. Studies reporting on the epidemiology, disease burden and treatment patterns in standard clinical care of primary IgAN in Europe are limited. This study assessed the epidemiology and outcomes among patients with primary IgAN using real-world data from the Netherlands.
Methods:
This retrospective cohort study used linked longitudinal data from the PHARMO Data Network in the Netherlands. Data of patients with biopsy-confirmed primary IgAN from the Dutch Nationwide Pathology Databank between 2010-2022 were linked to data from outpatient pharmacies and hospitals. IgAN incidence rates were estimated using national population data. Prevalence was calculated by proxy by multiplying incidence rate with the expected disease duration for IgAN. We calculated the incidence rate and prevalence for primary IgAN by proxy, by multiplying incidence and prevalence for IgAN by the proportion of patients with primary (versus secondary) IgAN found during selection of the study population. After linkage and excluding secondary forms of IgAN to identify primary IgAN we described the following outcomes at baseline or during follow-up: demographics, comorbidities, outpatient medication use, hospitalization rate, and mortality.
Results:
We identified 2,653 patients with biopsy-confirmed primary IgAN. Of these, 511 adult patients had linked data and 430 had primary IgAN (mean age 50±17 years; 31% female). The primary IgAN incidence rate was estimated to be 1.4/100,000 person-years, and the prevalence was estimated to be 37.7/100,000 persons. Median follow-up was 4.4 years (IQR: 1.9-7.6). Hematuria and hypertension were the most common hospitalization diagnoses at baseline. The following proportions of patients used medication at some point during follow-up: 43% for angiotensin-converting enzyme inhibitors (ACEi), 27% for angiotensin-receptor blockers (ARB), 61% for ACEi or ARB, 41% for glucocorticoids, 11% for mycophenolate mofetil, and 3% for cyclophosphamide. The hospitalization rate was 44,000/100,000 person-years (95% CI: 42,000-47,000), and the mortality rate was 1,400/100,000 person-years (95% CI: 900-2,000), with a median age at death of 76 years (IQR: 68-81).
Conclusions:
In this retrospective cohort study with linked real-world data, the incidence and prevalence estimates of primary IgAN in the Netherlands appear to be higher than what has been previously described for other European countries. More than one-third of patients were not treated with ACEi or ARB despite recommendations in international guidelines. These results underscore the disease burden experienced by patients with primary IgAN in the Netherlands. Future research focusing on disease progression and outcomes, such as changes in kidney function or end-stage kidney disease could provide further insight into the clinical burden of primary IgAN.
I have no potential conflict of interest to disclose.
I did not use generative AI and AI-assisted technologies in the writing process.