Association between the apolipoprotein B/albumin ratio and the risk of kidney stones in adults.

BACKGROUND: Kidney stones are widely considered a disease closely related to systemic metabolic disorders and systemic inflammation. The apolipoprotein B to albumin ratio (ApoB/Alb ratio) is a novel comprehensive biomarker that combines atherogenic lipid levels with systemic nutritional and inflammatory status. This study integrated data from two independent cohorts to explore the association between the serum ApoB/Alb ratio and the risk of kidney stones in adults. METHODS: The Chinese single-center retrospective cohort included 741 subjects (223 kidney stone patients and 518 healthy controls) evaluated from March 2022 to September 2025. For external validation, 12,108 adult participants from the US National Health and Nutrition Examination Survey (NHANES) database (2007-2016) were included. Multivariate logistic regression analysis evaluated the independent association, while restricted cubic spline (RCS) smoothing curve fitting explored the dose-response relationship. RESULTS: In the Chinese cohort, the serum ApoB/Alb ratio in the kidney stone group was significantly higher than in the control group (1.92 ± 0.52 vs. 1.84 ± 0.47, P = 0.048). After adjusting for comprehensive confounding factors, an elevated ApoB/Alb ratio was identified as a significant risk factor for kidney stones (OR = 3.26, 95% CI: 1.98-5.38). This significant positive association was highly consistent in the US NHANES validation cohort (OR = 1.30, 95% CI: 1.06-1.58). RCS analysis revealed a continuous positive linear dose-response relationship between the ApoB/Alb ratio and the prevalence of kidney stones in both cohorts. Furthermore, sensitivity and subgroup analyses demonstrated that this predictive value remains robust and is largely independent of traditional metabolic comorbidities such as hypertension and diabetes. CONCLUSION: As a comprehensive indicator of lipid metabolic disorders and inflammatory/nutritional imbalance, the ApoB/Alb ratio serves as a novel, highly sensitive, and reliable biomarker for predicting kidney stone risk.