Noninvasive markers track lupus disease activity, kidney damage
Combination of 2 measurements may improve detection: Study
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A combination of two simple lab tests may provide a noninvasive, more reliable way to assess disease activity in systemic lupus erythematosus (SLE) — the most common form of the autoimmune disorder lupus — and detect early kidney involvement, a study suggested.
Researchers found that blood levels of galectin-9, a protein that helps regulate immune responses, and urine levels of MCP-1, an immune signaling molecule, progressively increased with disease activity, suggesting they may serve as reliable indicators of disease severity. When used together, the two markers were more accurate than standard indicators in detecting lupus nephritis, a form of lupus marked by kidney damage.
“Combined assessment of [blood] galectin-9 and urine MCP-1 provides a non-invasive approach for evaluating overall disease activity in SLE and may facilitate early identification of [lupus nephritis],” the researchers wrote, adding that “compared to traditional indicators, this strategy had superior diagnostic accuracy.”
The study, “Clinical value of combined serum galectin-9 and urine MCP-1 testing for assessment of systemic lupus erythematosus disease activity and early diagnosis of lupus nephritis,” was published in the American Journal of Translational Research.
In lupus, the immune system mistakenly produces autoantibodies that attack the body’s own tissues, damaging multiple organs and causing a wide range of symptoms. Although the disease can affect nearly any part of the body, the kidneys are among the most commonly involved. About 60% of patients develop lupus nephritis, which remains a major cause of illness and death in this patient population.
Kidney involvement a challenge to detect
Still, assessing disease activity and detecting early kidney involvement remain challenging. Common scoring tools can lack precision, and early diagnosis of lupus nephritis typically requires a biopsy — an invasive procedure that carries risks and may not always capture early kidney changes.
“Therefore, there is an urgent need to identify reliable, noninvasive biomarkers for monitoring disease activity and facilitating early detection of [kidney] damage,” the researchers wrote.
Previous studies have suggested that galectin-9 levels in blood may reflect disease severity, while urinary MCP-1 levels have been recognized as a sensitive marker of kidney inflammation. However, their combined use in lupus has not been widely studied.
A team of researchers in China set out to investigate whether combining blood galectin-9 and urine MCP-1 testing could provide a more accurate, noninvasive way to monitor disease activity and enable early detection of lupus nephritis.
The team analyzed data from 148 people with SLE who were admitted to a hospital in China between June 2022 and May 2025. Participants were divided into three groups based on disease activity and kidney involvement: 48 had inactive disease, 40 had active disease without kidney involvement, and 60 had active disease with lupus nephritis.
Blood and urine samples were collected within 24 hours of hospital admission, and galectin-9 and MCP-1 levels were measured alongside standard laboratory markers.
Results showed that levels of both markers increased as disease activity worsened. Blood levels of galectin-9 rose progressively from patients with inactive disease to those with active disease and lupus nephritis. Urinary MCP-1 levels showed an even more marked increase, particularly in patients with kidney involvement.
Further statistical analysis showed that “in both groups of active SLE, galectin-9 and MCP-1 levels were positively correlated with disease activity, further supporting their use as reliable indicators for assessing overall SLE activity,” the researchers wrote.
When used together, the two markers performed better than either alone in identifying lupus nephritis. The combined approach also showed greater diagnostic accuracy than traditional markers, achieving an area under the curve (AUC) of 0.866, a measure of how well a test distinguishes between patients with and without a condition.
Even after adjusting for established predictors of lupus nephritis, both galectin-9 and MCP-1 remained independently associated with the condition, “highlighting their unique and cumulative clinical value,” the team wrote.
Higher MCP-1 levels were significantly associated with proliferative lupus nephritis, a more aggressive form of the disease, suggesting this marker may help distinguish between patients with more and less severe types of kidney involvement.
“This has significant clinical implications, as proliferative [lupus nephritis] is generally associated with a poor prognosis and often requires more aggressive immunosuppressive therapy,” the researchers wrote.
Together, the findings suggest “combined measurement of [blood] galectin-9 and urinary MCP-1 represents a promising noninvasive tool for assessing SLE disease activity and aiding the early diagnosis of [lupus nephritis],” the researchers concluded.
Still, they noted that the study was conducted at a single center and looked at biomarker levels at only one point in time. Larger, long-term studies are needed to confirm the findings and assess how these markers perform in routine clinical care, they said.
