People who have a lot of antibodies in their blood when they receive a lupus diagnosis are at greater risk of developing the kidney condition lupus nephritis later on, a South Korean study shows.
This finding could help doctors identify patients at risk of having lupus affect their kidneys, giving them a chance to come up with strategies to prevent kidney involvement.
Lupus nephritis, one of the most serious manifestations of systemic lupus erythematosus (SLE), affects up to 60% of lupus patients.
Because it affects the kidney’s ability to filter blood, the condition has a severe impact on patients’ lives. Early diagnosis and treatment is key to improving these patients’ outcomes.
Identifying patients at risk could help achieve this. But until this study, scientists had not come up with factors that could predict lupus nephritis.
Researchers at the University of Ulsan in Seoul wondered if levels of antibodies, or immunoglobulins, in the blood could be one factor. “Autoantibodies are central to the pathogenesis of SLE, and are typically present many years before SLE is diagnosed,” they wrote.
The team also was aware that many lupus patients have lower albumin levels in their blood. This prompted them to speculate that a low blood serum albumin-to-globulin ratio (AGR) could be a predictor of lupus nephritis.
The team analyzed the electronic medical records of 278 lupus patients who were diagnosed between January 2005 and December 2015. After a median of 44.9 months, 37 patients had developed lupus nephritis.
At diagnosis the lupus characteristics of patients who developed the kidney disease later was similar to those who did not. But these patients were younger, had lower serum albumin levels, lower AGR, and higher disease activity scores.
They also had higher levels of anti-dsDNA and anti-Sm antibodies, and lower levels of the lupus biomarkers complement 3 (C3) and 4 (C4), than patients who did not develop the kidney condition.
The team looked at which factors were significantly associated with the risk of lupus nephritis. They found that age and levels of C3, anti-dsDNA, anti-Sm, and AGR were all predictors of the condition.
But the presence of anti-Sm antibodies and AGR were the strongest predictors. While patients with Sm antobodies were twice as likely to develop lupus nephritis, those with low AGR were nearly five times more likely to have it.
“To the best of our knowledge, this is the first study to evaluate baseline risk factors at the time of initial SLE diagnosis for developing lupus nephritis,” the researchers wrote.
Low AGR values represent a greater proportion of globulins relative to total protein, which reflects higher amounts of antibodies in the blood of lupus patients, they wrote.