New Research Provides Insight Into Incidence, Prevalence of IgAN in the United States

Marc DeCongelio, MS

Credit: Marc DeCongelio on LinkedIn

Findings from a recent study are providing insight into the true incidence and prevalence of IgA nephropathy (IgAN) in the United States.¹

Based on large US-based claims datasets and pathologist input, the study estimates the overall annual incidence of IgAN is 2.1-2.2 per 100,000 and the total prevalence was 198,887-208,184 persons in 2021.¹

An autoimmune disease that occurs when clumps of antibodies are deposited in the kidneys, IgAN is one of the leading causes of glomerulonephritis and renal failure. Despite being a common disease, accurate prevalence data for IgAN are limited due to the need for a renal biopsy to establish the diagnosis as well as differences based on ethnicity, race, geography, and genetics.²

“While epidemiologic data is available from different global geographies, information related to the United States is limited to specific regions of the country,” Marc DeCongelio, MS, Associate Principal of Real World Evidence at Oracle Life Sciences, and colleagues wrote.¹

To develop a better understanding of the true incidence and prevalence of IgAN in the US, investigators collected primary data from board-certified pathologists who met the following inclusion criteria:

• Medical specialty in pathology
• ≥ 3 years in practice
• Examined ≥ 20 kidney biopsies in the past 12 months
• Examined ≥ 10 kidney biopsies with glomerulonephritis (GN) in the past 12 months
• Examined ≥ 1 kidney biopsy with GN that was classified as IgAN in the past 12 months
• Uses mesangial deposition of immunoglobulin A on immunofluorescence to diagnose IgAN

Respondents completed a web-based questionnaire between November and December 2021 describing their evaluation of kidney biopsies in the last 12 months, providing anonymized patient-level information from the charts of patients with biopsy-confirmed IgAN. Of note, their estimates were limited to a convenience sample of the 20 most recent charts per pathologist to mitigate respondent burden.¹

In total, 43 pathologists participated in the survey and evaluated a mean 169 (standard deviation [SD], 179.1) kidney biopsies in the preceding 12 months. Investigators noted the region of practice was uniformly distributed across US census regions.¹

Of 7267 total biopsies evaluated, 632 (8.7%) revealed IgAN. Among the biopsies with GN classified (mean, 64.1; SD, 70.5), IgAN was the most common (mean, 14.7; SD, 26.2).¹

To estimate disease incidence, investigators extrapolated the numbers of biopsies confirming IgAN and total biopsies from the survey to 2 large US claims databases, Komodo Health and Oracle Life Sciences, based on the total number of kidney biopsy claims and the total number of individuals found in the claims data during the same timeframe as the biopsy survey.¹

Based on the respective claims databases, investigators calculated annual incidence rates of 2.1 and 2.2 per 100,000.¹

Investigators then estimated the prevalence of IgAN by multiplying the incidence by disease duration determined from published literature, 28.5 years, yielding prevalence rates of 59.9 per 100,000 for Komodo Health and 62.7 per 100,000 for Oracle claims.¹

These estimates were validated against an additional data source, Oracle Life Sciences EHR. Of the 571 patient charts in the validation set, 176 had accessible biopsy results, 13 of which had a confirmed IgAN diagnosis.¹

Extrapolating to the total number of Oracle kidney biopsy claims and total individuals in the claims data, the incidence of IgAN was 1.9 per 100,000 and the prevalence was 54.2 per 100,000.¹

Based on prevalence estimates from the 2 main databases, the prevalence of IgAN extrapolated to the 2021 US population of 332,031,554 was:

• Komodo Health: (59.9/100,000) × 332,031,554 = 198,887 persons
• Oracle claims: (62.7/100,000) × 332,031,554 = 208,184 persons

Investigators acknowledged multiple limitations to these findings, some of which included the restricted availability of biopsy results; the potential capturing of repeated biopsies in individual patients; discordance in the years EHR records and claims and survey-based data were collected; and the inclusion of only patients with insurance.¹

“The current study estimates IgAN incidence of 2.1 and 2.2 per 100,000 and provides valuable epidemiologic data on IgAN in the U.S. that is consistent with earlier studies,” investigators concluded.¹ “Extrapolating prevalence from the current analysis to estimate the total prevalence for the U.S. provides a range of 198,887 to 208,184 persons for 2021.”

References

1. ^{DeCongelio M, Ali SN, Furegato M, et al. The incidence and prevalence of immunoglobulin A nephropathy in the United States. Clin Nephrol. doi:10.5414/CN111489}
2. ^{Rout P, Limaiem F, Hashmi MF. IgA Nephropathy (Berger Disease). StatPearls. April 22, 2024. Accessed January 14, 2025. https://www.ncbi.nlm.nih.gov/books/NBK538214/}