Investigators have created a nomogram to gauge lupus nephritis (LN) activity and inform the decision of whether to perform a kidney biopsy.
“There is no doubt that histopathological features are critical guidance for the management of LN, but it is an invasive procedure and its indications remain controversial,” Yi Yang, MD, of the Fourth Affiliated Hospital, Zhejiang University School of Medicine in Yiwu, Zhejiang, China, and colleagues wrote.
Using a training set of 235 patients with biopsy-proven LN, the investigators found significant differences in most laboratory tests between those with high- vs low-activity on kidney biopsy. Based on previous research, an activity index (AI) greater than 2 on biopsy defined the high activity group and an AI score less than 2 defined the low activity group.
“Patients with LN and a high AI have poor renal outcomes and high rates of nephritic relapse,” the investigators noted.
Multivariate analysis identified higher mean arterial pressure, lower estimated glomerular filtration rate, lower complement 3 level, higher urinary erythrocytes count, and anti-double-stranded DNA seropositivity as independent risk factors for high histologic activity in LN, Dr Yang’s team reported in Nephrology Dialysis Transplantation.
The investigators created a LASSO model based on some of these parameters. In a validation set of 102 patients, the model yielded a mean area under the curve of 0.896 for identifying patients with a high AI exceeding 2.
The investigators created a webtool based on the LASSO model that clinicians can use: https://ln-ai-calculator.com/
After inserting laboratory values, clinicians should choose the appropriate threshold. To determine whether to perform a biopsy or increase immunosuppressive therapy and disease surveillance, a risk score greater than 0.702 achieves 90% specificity. To avoid an unnecessary kidney biopsy, a risk score less than 0.507 has a 90.0% negative predictive value.
“This model is comparatively accurate and quantitative in distinguishing patients with a high histologic AI and possesses good external applicability,” the authors concluded.
The investigators plan to further refine the calculator with additional activity parameters, such as anti-double-stranded DNA titers, urinary erythrocytes count of different morphology, and novel biomarkers such as genes and metabolites. It may also incorporate pathologic features such as chronicity, thrombotic microangiopathy and anti-phospholipid syndrome nephropathy.
“A variety of clinical scenarios could be categorized and analysed, such as the diagnosis of patients with suspected LN, repeat kidney biopsies to evaluate disease activity and procedural biopsies,” according to Dr Yang’s team.