Study Highlights Evidence Gaps in IgA Nephropathy Disease Burden, Treatment Patterns

Kristin Pareja, PharmD, MPH

Credit: The Org

A recent literature review is calling attention to evidence gaps in IgA nephropathy (IgAN) epidemiology across select Asian Pacific countries.¹

The study was published in BMC Nephrology and highlighted a lack of incidence, mortality, treatment pattern, and humanistic burden data in certain countries across the Asia-Pacific region.¹

“While geographic variations of IgAN have been studied previously, few recent studies have focused on regional disease burden differences and treatment patterns among IgAN patients across Asian countries/regions and Australia,” Kristin Pareja, PharmD, MPH, director of global market access at Otsuka Pharmaceutical US, and colleagues wrote.¹

IgAN is the most common form of primary glomerulonephritis worldwide and is one of the leading causes of chronic kidney disease and end-stage renal disease (ESRD). Its exact cause is not known, but certain genetic and environmental factors are suspected to play a role. IgAN prevalence is thought to be greater across Asia and Europe, but regional disease burden differences and treatment patterns are not well understood across many countries.^1,2

Investigators sought to review and summarize evidence on IgAN prevalence, treatment patterns, and humanistic and economic burden in mainland China, Taiwan, South Korea, Japan, and Australia. The targeted literature review originally included relevant literature published from January 2010 to December 2021 but was later expanded to include studies from 2001.¹

Medline and Embase were the primary databases for publications in English, but other regional databases were searched for publications in local languages. Observational studies, reviews, and registry studies were included in the search. Publications that reported prevalence, incidence, mortality, treatment patterns, guidelines, economic, and humanistic burden were included for data extraction.¹

Studies that did not include outcomes of interest were excluded, as were studies with a sample size < 25. Investigators noted Strict predefined population, intervention, comparators, outcomes, and study design (PICOS) selection criteria and a Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) diagram were not used in this study.¹

In total, 69 publications and 3 clinical guidelines were included in the review. Of these, 38 were from mainland China, 15 were from Japan, 10 were from South Korea, 3 were from Taiwan, and 3 were from Australia. The majority (83%) of studies were retrospective in their design.¹

Evidence on IgAN incidence was available in 6 studies and ranged from 0 to 10.7 per 100,000 people per year in Australia, Japan, and Taiwan. Of note, the studies reported incidence across different patient populations. Among patients who underwent renal biopsy in mainland China, incidence ranged from 6.3% to 24.70%.¹

Prevalence across the general population was not reported in any of the included publications, except for one cross-sectional study that reported an IgAN prevalence rate of 0.03% among the general pediatric population.¹

In contrast, 35 publications detailed IgAN diagnosis rates. However, these figures varied greatly across studies and by country, ranging from 0 to 72.1% across mainland China, South Korea, Taiwan, Japan, and Australia.¹

Among the included studies, all-cause mortality was primarily reported as deaths due to ESRD, including 7 publications from mainland China, 7 from Korea, 4 from Japan, and 1 from Taiwan. However, investigators pointed out these studies varied in the definition of the endpoint, patient characteristics, and follow-up duration, making comparison difficult.¹

Treatment patterns were reported in 20 publications and 3 clinical guidelines. The top 3 commonly used therapies were angiotensin-converting enzyme inhibitor/angiotensin receptor blockers (0.9-99.6%), corticosteroids (3.5-100%), and immunosuppressants (1.6-85.5%) in Japan, mainland China, and South Korea.¹

Quality of life was reported in 4 publications from China and was not available for any other country included in the review. Among these studies, quality of life was measured by the 36-Item Short Form Health Survey, Daily Living Ability Rating Scale, and quality of life scale combined with Self-Rating Anxiety Scale and Self-Rating Depression Scale.¹

Although no publications reported indirect costs, 3 retrospective studies reported hospitalization costs for patients with IgAN in China. Results showed hospitalization costs ranged from $1284.73 to $2252.12.¹

Investigators outlined several potential limitations to these findings, including the varying sample sizes of the included publications, the potential for biases due to data not being weighed, and the single-center design of multiple included studies.¹

“The prevalence of IgA nephropathy among the general population in select Asian Pacific countries/regions is not commonly available, despite evidence from studies and clinical guidelines. In addition, it is observed across geographic regions that heterogeneity exists in prevalence rates, and large variations exist in treatment patterns,” investigators concluded.¹ “Future studies are needed to fill in these gaps to understand the contributing factors behind the differences through population-based, multi-center, and real-world studies.”

References:

1. ^{Zaidi O, Du F, Tang Z, Bhattacharjee S, Pareja K. Review on epidemiology, disease burden, and treatment patterns of IgA nephropathy in select APAC countries. BMC Nephrol. 2024;25(1):136. doi:10.1186/s12882-024-03555-5}
2. ^{National Institute of Health. IgA Nephropathy. Kidney Disease. September 2022. Accessed May 3, 2024. https://www.niddk.nih.gov/health-information/kidney-disease/iga-nephropathy#morelikely}