Association between different proportions of crescents and the progression of IgA nephropathy (IgAN): a systematic review and meta-analysis

Background: Immunoglobulin A nephropathy (IgAN) is a complex renal disease with a highly variable clinical course. Identifying reliable prognostic markers is crucial for risk stratification and treatment decisions. This study aimed to understand the influence of different proportions of crescents (Cs) on the progression of IgAN.

Methods: Four databases (PubMed, Web of Science, Embase, and Cochrane Library) were searched until September 25, 2023. The study encompassed IgAN patients, focusing on kidney outcomes and end-stage kidney disease (ESKD). Statistical analysis included calculating hazard ratios (HR) for binary outcomes and examining publication bias.

Results: The meta-analysis involved thirteen studies comprising 11,849 patients. For kidney outcomes, crescent formation may be linked to an elevated risk (HR = 2.01, 95%CI 1.40-2.87, P < 0.001). Furthermore, significantly increased risks of kidney outcomes were observed with a crescent proportion > 10 (HR = 1.8, 95%CI 1.32-2.45, P < 0.001) and > 25%(HR = 2.11, 95% CI 1.47-3.02, P < 0.001). Regarding ESKD, a proportion > 25% also displayed an elevated risk (HR = 1.70, 95% CI 1.18-2.44, P = 0.004). However, a proportion > 10% (including > 25%) did not show a significant association with ESKD (HR = 1.12, 95% CI 0.36-3.47, P = 0.842) versus less.

Conclusions: This systematic review and meta-analysis established a strong association between crescent proportions and the progression of IgAN. Higher proportions, notably exceeding 25%, were reliable prognostic markers, indicating a greater risk of adverse kidney outcomes and ESKD. These findings have significant clinical implications, offering the potential for more precise risk stratification in IgAN patients.