Lupus nephritis remains a common cause of morbidity and mortality in systemic lupus erythematosus (SLE). Current guidelines recommend performing a kidney biopsy at a urine protein-creatinine ratio of ≥0.5 g/g. However, cross-sectional studies reported a high prevalence of active histologic lupus nephritis lesions, and even chronic irreversible scarring, in patients with low-grade proteinuria. This study was initiated to assess disease progression in patients with SLE and low-grade proteinuria to identify risk factors for progression to overt proteinuria suggestive of clinical lupus nephritis.

Patients with SLE who had an incident urinary protein-creatinine ratio of ≥0.2 and <0.5 g/g without known lupus nephritis were identified from the Einstein Rheumatic Disease Registry. Patients who developed a random urinary protein-creatinine ratio of ≥0.5 g/g with or without biopsy during the follow-up period were defined as "progressors." Patients who progressed to a urinary protein-creatinine ratio of ≥0.5 g/g within 2 years of developing a urinary protein-creatinine ratio of ≥0.2 and <0.5 g/g were defined as "fast progressors," a subgroup expected to benefit most from early biopsies and therapeutic interventions.

Among 151 eligible patients with SLE and low-grade proteinuria at study entry, 76 (50%) progressed to a urinary protein-creatinine ratio of ≥0.5 g/g, of which 44 underwent a clinically indicated biopsy. The median (interquartile range) time from a urinary protein-creatinine ratio of ≥0.2 and <0.5 g/g to progression was 1.2 (0.3–3.0) years. Of the 20 biopsies performed in the first 2 years, 16 specimens showed active, treatable lupus nephritis. Low complement and shorter SLE duration at low-grade proteinuria onset were associated with progression to overt proteinuria across different analyses. Other associated factors included hypertension, diabetes mellitus, younger age, and the presence of hematuria.

In this longitudinal cohort of patients with SLE and low-grade proteinuria at study entry, over half progressed to a urinary protein-creatinine ratio of ≥0.5 g/g in a short time period.

狼疮性肾炎仍然是系统性红斑狼疮（SLE）发病和死亡的常见原因。目前的指南建议在尿蛋白肌酐比≥0.5 g/g 时进行肾活检。然而，横断面研究报告称，低度蛋白尿患者中活动性组织学狼疮肾炎病变的患病率很高，甚至慢性不可逆转的疤痕形成。本研究旨在评估 SLE 和低度蛋白尿患者的疾病进展，以确定进展为提示临床狼疮性肾炎的明显蛋白尿的危险因素。

从爱因斯坦风湿病登记处筛选出尿蛋白肌酐比值≥0.2且<0.5 g/g且无已知狼疮性肾炎的 SLE 患者。在随访期间，无论是否进行活检，随机尿蛋白肌酐比率≥0.5 g/g的患者被定义为“进展者”。尿蛋白肌酐比值≥0.2且<0.5g/g后2年内进展至尿蛋白肌酐比值≥0.5g/g的患者被定义为“快速进展者”，预计受益最多的亚组来自早期活检和治疗干预。

在 151 名符合研究入组时患有 SLE 和低度蛋白尿的患者中，76 名 (50%) 进展至尿蛋白肌酐比值≥0.5 g/g，其中 44 名患者接受了有临床指征的活检。从尿蛋白肌酐比值≥0.2且<0.5 g/g到进展的中位时间（四分位距）为1.2（0.3-3.0）年。在前 2 年进行的 20 例活检中，16 例显示活动性、可治疗的狼疮性肾炎。在不同的分析中，低度补体和低度蛋白尿发作时较短的 SLE 持续时间与进展为明显蛋白尿有关。其他相关因素包括高血压、糖尿病、年龄较小和存在血尿。

在研究开始时患有 SLE 和低度蛋白尿的纵向队列中，超过一半的患者在短时间内尿蛋白肌酐比值≥0.5 g/g。