The prevalence of immunoglobulin A nephropathy in the European Union and the impact of the COVID-19 pandemic: an estimation approach utilizing the kidney biopsy frequency.

Background: Immunoglobulin A nephropathy (IgAN) is the most common type of primary glomerulonephritis, requiring a kidney biopsy for diagnosis. This study aimed to estimate the prevalence of primary IgAN within the European Union (EU) and investigate the potential impact of the coronavirus disease 2019 (COVID-19) pandemic on kidney biopsy rates and IgAN diagnosis frequency.

Methods: We conducted four comprehensive literature searches to identify data on the IgAN prevalence and incidence, native kidney biopsy rates and COVID-19 impact on these metrics. We calculated country-specific prevalence estimates based on a combination of published and modeled data, incorporating biopsy frequency and the Healthcare Access and Quality Index (HAQI). The EU IgAN prevalence was derived from country-specific prevalence estimates weighted by population size.

Results: The estimated prevalence of IgAN in the EU was 4.31 per 10 000 population, with large geographic variation among countries, ranging from 0.16 to 14.4 per 10 000 population. A strong correlation was observed between the IgAN incidence and biopsy rate (R = 0.96). Countries with a higher HAQI mostly exhibited higher biopsy rates and IgAN incidences. The COVID-19 pandemic resulted in a notable decrease in kidney biopsy rates for most European countries with available information in 2020 compared with both pre- and post-pandemic periods. However, the long-term implications of this reduction on biopsy rates and subsequent IgAN incidence remain to be determined.

Conclusion: Our findings confirm the rarity of IgAN, albeit the most common type of glomerulonephritis. They underscore a robust correlation between biopsy rates and IgAN incidence, influenced by healthcare access and quality. The COVID-19 pandemic's temporary suppression of biopsy rates in 2020 suggests potential delays in IgAN diagnosis, warranting further investigation into the long-term effects.