The association between NPAR and proteinuria.

Introduction
The neutrophil-percentage-to-albumin ratio (NPAR), a novel inflammatory biomarker, has been used to predict the prognosis of patients with cancer and cardiovascular disease. However, the relationship between NPAR and chronic kidney disease (CKD) remains unknown. The purpose of this study was to investigate the possible association between NPAR and CKD.
Methods
The cross-sectional study included participants with complete information on NPAR, serum creatinine (Scr), or urinary albumin-to-creatinine ratio (UACR) from the 2009–2018 National Health and Nutrition Examination Survey (NHANES). CKD was defined as the presence of either low estimated glomerular filtration rate (eGFR) or albuminuria. Univariate and multivariate logistic regression and restricted cubic spline regression were used to assess the linear and nonlinear associations between NPAR and renal function. Subgroup and interactive analyses were performed to explore potential interactive effects of covariates. Missing values were imputed using random forest.
Results
A total of 25,236 participants were enrolled in the study, of whom 4518 (17.9%) were diagnosed with CKD. After adjustment for covariates, the odds ratios (ORs) for prevalent CKD were 1.19 (95% CI = 1.07–1.31, p <0.05) for the Q2 group, 1.53 (95% CI = 1.39–1.69, p < 0.001) for the Q3 group, and 2.78 (95% CI = 2.53–3.05, p < 0.001) for the Q4 group. There was a significant interaction between age and diabetes mellitus on the association between NPAR and CKD (both p for interaction < 0.05). And there was a non-linear association between NPAR levels and CKD in the whole population (p for non-linear < 0.001). All sensitivity analyses supported the positive association between NPAR and CKD.
Conclusions
NPAR was positively correlated with increased risk of CKD. The NPAR may serve as an available and cost-effective tool for identifying and intervening the individuals at risk of CKD.

Introduction
中性粒细胞百分比与白蛋白比值（neutrophil-percentage-to-albumin ratio, NPAR）是一种新型炎症生物标志物，已被用于预测癌症与心血管疾病患者的预后。然而，NPAR与慢性肾脏病（chronic kidney disease, CKD）之间的关联仍未明确。本研究旨在探讨NPAR与CKD之间可能存在的关联。
Methods
本横断面研究纳入了2009–2018年全国健康与营养检查调查（National Health and Nutrition Examination Survey, NHANES）中，具备NPAR、血清肌酐（serum creatinine, Scr）与尿白蛋白肌酐比（urinary albumin-to-creatinine ratio, UACR）完整数据的参与者。CKD定义为估算肾小球滤过率（estimated glomerular filtration rate, eGFR）降低或存在白蛋白尿。本研究采用单因素、多因素logistic回归以及限制性立方样条回归，分析NPAR与肾功能之间的线性及非线性关联。通过亚组分析与交互作用分析，探索协变量的潜在交互效应。缺失值采用随机森林法进行插补。
Results
本研究共纳入25236名参与者，其中4518名（17.9%）被诊断为CKD。校正协变量后，Q2组、Q3组与Q4组人群的现患CKD比值比（odds ratios, OR）分别为1.19（95%置信区间CI：1.07–1.31，p<0.05）、1.53（95%CI：1.39–1.69，p<0.001）与2.78（95%CI：2.53–3.05，p<0.001）。年龄与糖尿病在NPAR与CKD的关联中存在显著交互作用（交互项p均<0.05）。全人群中，NPAR水平与CKD呈非线性关联（非线性检验p<0.001）。所有敏感性分析均证实NPAR与CKD之间存在正向关联。
Conclusions
NPAR与CKD发病风险升高呈正相关。NPAR或可作为一种便捷且具有成本效益的工具，用于识别并干预CKD高风险人群。