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

Abstract

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 (R2 = 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.