A study recently published in the journal Arthritis & Rheumatology revealed that proteinuria is an accurate clinical predictor of long-term renal outcome in patients with lupus nephritis. The study was conducted by an international research team and is entitled “Predictors of Long-Term Renal Outcome in Lupus Nephritis Trials: Lessons Learned from the Euro-Lupus Nephritis Cohort.”
Systemic lupus erythematosus (SLE) is a severe autoimmune disease in which the body’s own immune system is abnormally activated leading to an attack of healthy joints and organs, resulting in inflammation, swelling, pain, disability and often in tissue destruction and multi-organ damage. When the immune system attacks the kidney it becomes inflamed, a process known as lupus nephritis, one of the most severe complications in SLE patients that can lead to long-term damage, kidney failure and death. There is no approved drug treatment for lupus nephritis.
In order to conduct proper lupus nephritis trials, it is necessary to establish which response measures are the most predictive in terms of good long-term kidney function. In the study, researchers assessed whether proteinuria (the excess of serum proteins in the urine), serum creatinine (Cr, a product of muscle metabolism) and urinary red blood cells (RBCs) could be used as accurate clinical predictors of good long-term renal outcome (defined as a serum Cr value ≤ 1.0 mg/dL).
The research team analyzed data available from 76 patients in the Euro-Lupus Nephritis Trial, who had 3, 6, or 12 months measurements of proteinuria, serum Cr and urinary RBC, with a minimum follow-up period of 7 years. The specificity and sensitivity of each biomarker was determined.
Researchers found that the best clinical predictor of good long-term renal function at 7 years was proteinuria with a value of < 0.8 gm/day at 12 months, with a sensitivity of 81% and specificity of 78%. Combining proteinuria and serum Cr as a composite predictor had no benefit in terms of improving sensitivity and specificity, while the combination of urinary RBCs significantly decreased sensitivity to 47%.
The research team concluded that the level of proteinuria at 12 months is the best single predictor of long-term renal outcome in patients with lupus nephritis. Researchers also suggest that since urinary RBCs have a poor predictive value, they should not be considered as a response measure in clinical trials for lupus nephritis.